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First Digit Four (Posted on 2009-08-08) Difficulty: 2 of 5
Determine the total number of base ten positive integers having the form 2N with the first digit (from the left) being 4, where N is a positive integer < 333.

See The Solution Submitted by K Sengupta    
Rating: 5.0000 (1 votes)

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mathematica solution | Comment 1 of 3

it was a simple matter to find all 33 solutions with mathematica and they are:

2^2=4
2^12=4096
2^22=4194304
2^32=4294967296
2^42=4398046511104
2^52=4503599627370496
2^62=4611686018427387904
2^72=4722366482869645213696
2^82=4835703278458516698824704
2^92=4951760157141521099596496896
2^105=40564819207303340847894502572032
2^115=41538374868278621028243970633760768
2^125=42535295865117307932921825928971026432
2^135=43556142965880123323311949751266331066368
2^145=44601490397061246283071436545296723011960832
2^155=45671926166590716193865151022383844364247891968
2^165=46768052394588893382517914646921056628989841375232
2^175=47890485652059026823698344598447161988085597568237568
2^185=49039857307708443467467104868809893875799651909875269632
2^198=401734511064747568885490523085290650630550748445698208825344
2^208=411376139330301510538742295639337626245683966408394965837152256
2^218=421249166674228746791672110734681729275580381602196445017243910144
2^228=431359146674410236714672241392314090778194310760649159697657763987456
2^238=441711766194596082395824375185729628956870974218904739530401550323154944
2^248=452312848583266388373324160190187140051835877600158453279131187530910662656
2^258=463168356949264781694283940034751631413079938662562256157830336031652518559744
2^268=474284397516047136454946754595585670566993857190463750305618264096412179005177856
2^278=485667223056432267729865476705879726660601709763034880312953102434726071301302124544
2^288=497323236409786642155382248146820840100456150797347717440463976893159497012533375533056
2^301=4074071952668972172536891376818756322102936787331872501272280898708762599526673412366794752
2^311=4171849679533027504677776769862406473833407270227837441302815640277772901915313574263597826048
2^321=4271974071841820164790043412339104229205409044713305539894083215644439451561281100045924173873152
2^331=4374501449566023848745004454235242730706338861786424872851541212819905998398751846447026354046107648


  Posted by Daniel on 2009-08-08 12:40:02
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