A268228 a(n) = sum of digits of (2n + 1)^2.

1, 9, 7, 13, 9, 4, 16, 9, 19, 10, 9, 16, 13, 18, 13, 16, 18, 10, 19, 9, 16, 22, 9, 13, 7, 9, 19, 10, 18, 16, 13, 27, 13, 25, 18, 10, 19, 18, 25, 13, 18, 31, 16, 27, 19, 19, 27, 16, 22, 18, 4, 16, 9, 19, 19, 9, 25, 13, 27, 13, 16, 18, 19, 19, 18, 16, 31, 18, 31, 16, 27, 19, 10, 18, 7, 13, 18

Offset: 0

Author

N. J. A. Sloane, Jan 31 2016

Keywords

• nonn
• base

Links

• Robert Israel, Table of n, a(n) for n = 0..10000
• H. I. Okagbue, M. O. Adamu, S. A. Iyase, A. A. Opanuga, Sequence of Integers Generated by Summing the Digits of their Squares, Indian Journal of Science and Technology, Vol 8(15), DOI: 10.17485/ijst/2015/v8i15/69912, July 2015.

Crossrefs

Bisection of A004159. Cf. A007953, A016754, A268227.

Programs

Magma

[&+Intseq((2*n+1)^2): n in [0..87] ]; // Vincenzo Librandi, Jul 23 2016

Maple

f:= n -> convert(convert((2*n+1)^2,base,10),`+`):
map(f, [$0..100]); # Robert Israel, Apr 26 2020

Mathematica

Table[Sum[DigitCount[(2 n + 1)^2] [[i]] i, {i, 9}], {n, 0, 70}] (* Vincenzo Librandi, Jul 23 2016, after G. C. Greubel *)

PARI

a(n) = sumdigits((2*n+1)^2); \\ Michel Marcus, Jul 23 2016

Formula

a(n) = A007953(A016754(n)). - Michel Marcus, Oct 13 2017