A269247 Number of times the digit 7 appears in the decimal expansion of n^3.

0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 2, 0, 0, 0, 1, 1, 1, 1, 0, 1, 0, 0, 1, 0, 0, 0, 1, 2, 0, 0, 1, 0, 0, 1, 0, 0, 0, 2, 1, 1, 1, 0, 0, 1, 0, 0, 0, 1, 0, 1, 1, 1, 0, 0, 0, 1, 1, 1, 0, 1, 1, 0, 1, 0, 0, 0, 0, 3, 1, 0, 0, 0, 1, 1, 1, 2, 2, 1, 0, 2, 1, 1, 0, 1, 0

Offset

0,27

Comments

The cubes corresponding to the first occurrence of 1, 2, 3, ... are listed in A036534, i.e., A036534(n)^(1/3) = A048372(n) is the index of the first occurrence of n.

Links

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

Example

0^3 = 0, 1^3 = 1, 2^3 = 8 and 4^3 = 64 all have a(0) = a(1) = a(2) = a(4) = 0 digits '7'.
3^3 = 27 has a(3) = 1 digit '7'.

Mathematica

Table[DigitCount[n^3, 10, 7], {n, 0, 100}] (* Robert Price, Mar 21 2020 *)

Prog

(PARI) A269247(n)=#select(t->t==7, digits(n^3))

Crossrefs

Cf. A036534 and A036527 - A036536; A048372 and A048365 - A048374.

Analog for the other digits 0, 1, ..., 9: A269250, A269241, A269242, A269243, A269244, A269245, A269246, A269247, A269248, A269249.

Analog for squares: A086015 (digit 7), and A086008 - A086017 for digits 0 - 9.

Sequence in context: A360115 A341025 A364044 * A330268 A089310 A129753

Adjacent sequences: A269244 A269245 A269246 * A269248 A269249 A269250

Keyword

nonn,base

Author

M. F. Hasler, Feb 20 2016

Status

approved