A033107 Number of 7's when n is written in base b for 2<=b<=n+1.

0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 2, 1, 2, 1, 3, 1, 2, 2, 2, 1, 3, 1, 3, 2, 2, 1, 4, 1, 2, 2, 4, 1, 3, 1, 3, 3, 2, 1, 5, 2, 4, 3, 4, 2, 5, 3, 6, 3, 3, 2, 7, 2, 3, 5, 6, 3, 5, 2, 4, 3, 6, 3, 9, 2, 3, 4, 4, 4, 6, 3, 8, 4, 3, 2

Offset: 1

Author

Clark Kimberling

Keywords

• nonn
• base
• look

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A033093, A033095, A033097, A033099, A033101, A033103, A033105, A033108, A033109, A033111.

Programs

Maple

f:= proc(n) local b;`+`(seq(numboccur(7,convert(n,base,b)),b=8..n+1)) end proc:
map(f, [$1..100]); # Robert Israel, Aug 20 2024

Mathematica

f[n_] := Count[Flatten@ Table[ IntegerDigits[n, b], {b, 2, n + 1}], 7]; Array[f, 90] (* Robert G. Wilson v, Nov 14 2012 *)