login
A214515
Numbers of the form p^2 + q^2 + r^2 + s^2, where p, q, r, and s are primes.
4
16, 21, 26, 31, 36, 37, 42, 47, 52, 58, 61, 63, 66, 68, 71, 76, 79, 82, 84, 87, 92, 100, 103, 106, 108, 111, 116, 124, 127, 132, 133, 138, 143, 148, 151, 154, 156, 159, 164, 172, 175, 178, 180, 181, 183, 186, 188, 191, 196, 199, 202, 204, 207, 212, 220, 223
OFFSET
1,1
MATHEMATICA
nn = 10^3; ps = Prime[Range[PrimePi[Sqrt[nn]]]]; t = Flatten[Table[ps[[i]]^2 + ps[[j]]^2 + ps[[k]]^2 + ps[[l]]^2, {i, Length[ps]}, {j, i, Length[ps]}, {k, j, Length[ps]}, {l, k, Length[ps]}]]; t = Select[t, # <= nn &]; Union[t]
CROSSREFS
Cf. A045636 (two primes), A214514 (three primes).
Sequence in context: A180411 A050436 A038868 * A270783 A330591 A302167
KEYWORD
nonn
AUTHOR
T. D. Noe, Jul 29 2012
STATUS
approved