OFFSET
1,8
COMMENTS
a(n) is the number of primes p < n such that n-p has a prime factor > p.
a(n) <= A056172(n-1), with equality for n = 1, 2, 3, 4, 5, 8, 24.
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
a(8) = 2 because 2 = 8 mod 3 and 3 = 8 mod 5.
MAPLE
f:= proc(n) local k; nops(select(isprime, {seq(n mod k, k=select(isprime, [$2..n-1]))})) end proc:
map(f, [$1..100]);
CROSSREFS
KEYWORD
nonn,look
AUTHOR
J. M. Bergot and Robert Israel, Feb 01 2021
STATUS
approved