cp's OEIS Frontend

A256270 a(1) = 1; for n > 1, a(n) is the smallest positive integer not already in the sequence such that a(1)^2 + a(2)^2 + ... + a(n)^2 is prime.

%I A256270 #18 Jun 18 2015 05:52:08
%S A256270 1,2,6,24,12,54,18,36,30,48,60,84,42,90,66,72,96,78,120,126,102,150,
%T A256270 144,108,156,114,138,132,180,204,210,168,186,192,234,174,162,216,198,
%U A256270 222,246,228,264,348,240,270,300,330,336,402,390,414,288,306,258,294,318,324,276,252,372,426,366,282,432,354,378
%N A256270 a(1) = 1; for n > 1, a(n) is the smallest positive integer not already in the sequence such that a(1)^2 + a(2)^2 + ... + a(n)^2 is prime.
%C A256270 1 is the only odd number in this sequence.
%C A256270 Excluding 1 and 2, this is a permutation of the positive multiples of 6.
%F A256270 a(n)^2 = A073852(n).
%o A256270 (PARI) v=[1];n=1;while(n<10^3,if(isprime(n^2+sum(i=1,#v,v[i]^2))&&!vecsearch(vecsort(v),n),v=concat(v,n);n=1);n++);v
%Y A256270 Cf. A073659, A073852.
%K A256270 nonn,easy
%O A256270 1,2
%A A256270 _Derek Orr_, Jun 01 2015