A079130 - OEIS

%I #19 Sep 05 2014 02:55:46

%S 13,19,31,37,67,73,103,109,127,139,157,163,181,193,199,211,229,271,

%T 283,307,337,373,379,397,409,433,463,487,499,523,541,571,577,607,613,

%U 631,643,661,733,739,751,757,769,787,811,823,829,859,877,883,919,937,967

%N Primes such that iterated sum-of-digits (A038194) is a square.

%C Primes which are 1 or 4 mod 9. - _Charles R Greathouse IV_, Sep 04 2014

%H Harvey P. Dale, <a href="/A079130/b079130.txt">Table of n, a(n) for n = 1..1000</a>

%F a(n) ~ 3n log n. - _Charles R Greathouse IV_, Sep 04 2014

%p select(isprime,map(t -> (9*t+1,9*t+4),[$1..1000]));  # _Robert Israel_, Sep 04 2014

%t sQ[n_]:=MemberQ[{1,4,9},NestWhile[Total[IntegerDigits[#]]&,n,#>9&]]; Select[Prime[Range[300]],sQ] (* _Harvey P. Dale_, Dec 06 2012 *)

%o (PARI) forprime(p=2,1000,if(issquare(p%9),print1(p,",")))

%Y Cf. A078403, A079131, A079132.

%K nonn,easy,base

%O 1,1

%A _Klaus Brockhaus_, Dec 28 2002