A126209 Number of 7's in decimal expansion of 7^n.

0, 1, 0, 0, 0, 1, 1, 0, 1, 1, 1, 3, 1, 1, 2, 2, 0, 2, 1, 1, 3, 1, 0, 3, 0, 1, 4, 1, 2, 5, 1, 4, 2, 7, 1, 4, 4, 4, 3, 0, 3, 3, 3, 3, 5, 4, 1, 2, 2, 6, 2, 3, 5, 6, 6, 5, 7, 6, 6, 7, 4, 7, 5, 5, 6, 6, 3, 8, 1, 3, 7, 6, 8, 6, 7, 7, 1, 5, 7, 5, 4, 9, 7, 6, 10, 7, 7, 7, 4, 14, 8, 5, 10, 8, 10, 13, 11, 6, 7, 6, 6

Offset

0,12

Links

Table of n, a(n) for n=0..100.

Maple

P:=proc(n) local i, k, x, y, w, cont; y:=7; k:=y; for i from 0 by 1 to n do x:=y^i; cont:=0; while x>0 do w:=x-trunc(x/10)*10; if w=k then cont:=cont+1; fi; x:=trunc(x/10); od; print(cont); od; end: P(100);

Mathematica

DigitCount[7^Range[0, 100], 10, 7] (* Harvey P. Dale, Sep 03 2015 *)

Crossrefs

Cf. A065710, A126205, A126206, A126207, A126208, A126210, A126211.

Sequence in context: A089338 A356400 A153066 * A176346 A338878 A073166

Adjacent sequences: A126206 A126207 A126208 * A126210 A126211 A126212

Keyword

base,nonn

Author

Paolo P. Lava and Giorgio Balzarotti, Dec 20 2006

Status

approved