A339327 a(n) = (A001414(prime(n)-1)*A001414(prime(n)+1)) mod prime(n).

0, 2, 0, 2, 5, 11, 13, 15, 2, 23, 7, 25, 9, 8, 40, 28, 18, 30, 1, 26, 30, 76, 21, 43, 14, 5, 6, 73, 16, 21, 83, 98, 96, 31, 19, 73, 50, 141, 24, 41, 112, 149, 8, 134, 145, 105, 125, 45, 39, 93, 36, 177, 143, 38, 254, 30, 60, 129, 75, 93, 221, 291, 243, 214, 55, 59, 172, 167, 54, 335, 285, 205

Offset

1,2

Comments

a(n)=1 for n=19 and 7476. Are there others?

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

a(4) = (A001414(6)*A001414(8)) mod 7 = (5*6) mod 7 = 2.

Maple

spf:= proc(n) add(t[1]*t[2], t=ifactors(n)[2]) end proc:
f:= proc(n) local p;
  p:= ithprime(n);
  spf(p-1)*spf(p+1) mod p
end proc:
map(f, [$1..100]);

Crossrefs

Cf. A001414.

Sequence in context: A175631 A243816 A243159 * A258144 A113772 A033716

Adjacent sequences: A339324 A339325 A339326 * A339328 A339329 A339330

Keyword

nonn,look

Author

J. M. Bergot and Robert Israel, Nov 30 2020

Status

approved