Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #13 Aug 19 2019 17:24:19
%S 1,6,5,10,3,2,8,7,13,20,30,28,27,26,35,58,45,56,55,21,96,142,53,93,
%T 262,14,139,12,195,47,87,57,214,404,133,255,81,252,37,36,187,128,127,
%U 479,75,572,477,313,70,475,179,68,241,310,19,98,115,469,762,114,234,94,302,231,1238,229,298,376,50,161
%N First appearance of prime(n) in A157480.
%C Apparently all primes eventually appear in A157480. Note that this sequence is one-to-one map while A157480 not.
%F A157480(a(n)) = prime(n), or prime(a(n))+prime(n) is a square.
%e a(3)=5 because A157480(5)=prime(3)=5 and prime(3)+prime(5)=5+11=16=4^2,
%e a(4)=10 because A157480(10)=prime(4)=7 and prime(4)+prime(10)=7+29=36=6^2.
%Y Cf. A157480.
%K nonn
%O 1,2
%A _Zak Seidov_, Dec 10 2014