# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a224966 Showing 1-1 of 1 %I A224966 #12 Sep 27 2013 10:57:25 %S A224966 1,4,10,16,31,32,40,41,43,62,71,76,94,95,97,98,121,142,158,163,164, %T A224966 166,179,188,208,211,214,227,229,259,260,265,284,301,313,317,320,328, %U A224966 331,340,352,355,356,365,380,382,386,392,397,401,418,424,425,431,436,439 %N A224966 Numbers n such that n^2+sum-of-digits(n^2) is prime. %C A224966 This is the sequence of indices of prime numbers in A171613. %C A224966 The Ulam spiral for this sequence is a near-perfect line y=-x (see links). %H A224966 Christian N. K. Anderson, Table of n, a(n) for n = 1..10000 %H A224966 Christian N. K. Anderson, The Ulam Spiral for the prime numbers derived from this sequence, i.e. a(n)^2+sum of digits(a(n)^2) %e A224966 a(12)=76 because 76^2=5776, and 5776+(5+7+7+6)=5801, which is prime. %o A224966 (R) library(gmp); digsum<-function(x) sum(as.numeric(unlist(strsplit(as.character(x),split="")))) %o A224966 ans=as.bigz(rep(0,100)); n=1; i=as.bigz(1) %o A224966 while(n<=100) { %o A224966 if(isprime((w=i^2+digsum(i^2)))) ans[(n=n+1)-1]=i %o A224966 i=i+1 %o A224966 }; ans %Y A224966 Cf. A048521. %Y A224966 Cf. numbers of the form n^2+sum-of-digits(n^2) A171613, and subsets A171614, A171615. %Y A224966 Cf. A062028. %K A224966 nonn,base %O A224966 1,2 %A A224966 _Kevin L. Schwartz_ and _Christian N. K. Anderson_, Apr 21 2013 # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE