OFFSET
1,3
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = A259194(4*n). - Robert Israel, Oct 29 2019
EXAMPLE
4*3 = 12 = 2+2+3+5 = 3+3+3+3 hence a(3)=2.
MAPLE
N:= 400: # to get a(0) to a(N/4)
Primes:= select(isprime, [$1..N]):
np:= nops(Primes):
for j from 0 to np do g[0, j]:= 1 od:
for n from 1 to 4 do
g[n, 0]:= 0:
for j from 1 to np do
g[n, j]:= convert(series(add(g[k, j-1]
*x^((n-k)*Primes[j]), k=0..n), x, N+1), polynom)
od
od:
seq(coeff(g[4, np], x, 4*i), i=1..N/4); # Robert Israel, Oct 29 2019
PROG
(PARI) a(n)={my(s=0); forprime(i=2, n, forprime(j=i, (4*n-i)\3, forprime(k=j, (4*n-i-j)\2, if(isprime(4*n-i-j-k), s++)))); s} \\ Andrew Howroyd, Oct 29 2019
CROSSREFS
KEYWORD
nonn,look
AUTHOR
Benoit Cloitre, May 14 2002
EXTENSIONS
Corrected by Robert Israel, Oct 29 2019
STATUS
approved