A107289 - OEIS

%I #8 Jan 09 2019 01:53:35

%S 4,5,7,16,17,25,26,28,29,32,34,37,38,40,44,47,49,50,52,53,56,61,62,64,

%T 65,70,73,79,82,83,89,91,98,106,107,109,115,116,118,119,125,127,133,

%U 137,142,143,146,149,151,154,155,160,161,164,170,173,181,182,187,188,199

%N Numbers k such that the sum of digits of k^2 is a prime.

%F a(n) = sqrt(A065408(n)).

%t bb={};Do[If[PrimeQ[Apply[Plus, IntegerDigits[n^2]]], bb=Append[bb, n]], {n, 500}];bb

%o (PARI) isok(n) = isprime(sumdigits(n^2)); \\ _Michel Marcus_, Jan 09 2019

%Y Cf. A065408.

%K nonn,base

%O 1,1

%A _Zak Seidov_, May 20 2005