A269242 - OEIS

%I #25 Sep 08 2022 08:46:15

%S 0,0,0,1,0,1,1,0,1,1,0,0,1,1,1,0,0,0,1,0,0,1,0,1,1,1,0,0,2,1,1,1,1,0,

%T 0,1,0,0,1,0,0,1,0,0,0,1,0,1,1,0,1,1,0,0,0,0,0,0,1,1,1,2,2,1,2,2,1,0,

%U 1,1,0,0,1,0,2,1,0,0,1,0,1,0,0,0,1,1,0,0,1,0,1,0,0,0,0,0,0,1

%N Number of times the digit 2 appears in the decimal expansion of n^3.

%C The cubes corresponding to the first occurrence of 1, 2, 3, ... are listed in A036529, i.e., A036529(n)^(1/3) = A048367(n) is the index of the first occurrence of n.

%H Robert Israel, <a href="/A269242/b269242.txt">Table of n, a(n) for n = 0..10000</a>

%e 0^3 = 0 has a(0) = 0 digits '2'.

%e 1^3 = 1 has a(1) = 0 digits '2'.

%e 2^3 = 8 has a(2) = 0 digits '2'.

%e 3^3 = 27 has a(3) = 1 digits '2'.

%e 4^3 = 64 has a(4) = 0 digits '2'.

%e 5^3 = 125 has a(5) = 1 digit '2'.

%e 28^3 = 21952 is the least cube which has a(28) = 2 digits '2'.

%p seq(numboccur(2,convert(n^3,base,10)),n=0..100); # _Robert Israel_, Jan 26 2020

%t Table[DigitCount[n^3, 10, 2], {n, 0, 100}] (* _Robert Price_, Mar 21 2020 *)

%o (PARI) A269242(n)=#select(t->t==2,digits(n^3))

%o (Magma) [Multiplicity(Intseq(n^3),2): n in [0..100]]; // _Marius A. Burtea_, Jan 26 2020

%Y Cf. A036529 and A036527 - A036536; A048367 and A048365 - A048374.

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

%Y Analog for squares: A086010 (digit 2), and A086008 - A086017 for digits 0 - 9.

%K nonn,base

%O 0,29

%A _M. F. Hasler_, Feb 20 2016