OFFSET
1,4
LINKS
Altug Alkan, Table of n, a(n) for n = 1..10000
EXAMPLE
a(4) = 2 because 4^4 + 1^4 = 257 and 4^4 + 3^4 = 337 are prime numbers.
MATHEMATICA
f[n_] := Block[{b = Mod[n, 2] + 1, c = 0}, While[b < n, If[ Mod[n^4 + b^4, 16] == 1 && PrimeQ[n^4 + b^4], c++]; b++]; c]; f[1] = 1; Array[f, 90]
PROG
(PARI) a(n) = if(n==1, 1, sum(k=1, n-1, isprime(n^4+k^4)));
(PARI) first(n)=my(v=vector(n), n4); for(N=1, n, n4=N^4; forstep(k=N%2+1, N, 2, if(isprime(n4+k^4), v[N]++))); v[1]++; v \\ Charles R Greathouse IV, Feb 27 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert G. Wilson v and Altug Alkan, Feb 26 2017
STATUS
approved