A218491 Number of ways that prime(n) can be represented as the sum of four nonzero squares.

0, 0, 0, 1, 0, 1, 0, 1, 1, 0, 2, 2, 0, 2, 2, 1, 1, 2, 3, 2, 3, 3, 2, 1, 4, 1, 5, 2, 3, 2, 5, 2, 3, 4, 2, 5, 6, 6, 5, 3, 3, 5, 5, 6, 4, 7, 5, 9, 5, 7, 4, 6, 6, 5, 5, 7, 4, 9, 8, 4, 9, 6, 10, 8, 10, 7, 9, 9, 7, 9, 8, 9, 13, 10, 10, 11, 7, 13, 7, 10, 8, 11, 10, 13

Offset: 1

Author

Arkadiusz Wesolowski, Nov 02 2012

Keywords

• nonn

Comments

a(pi(A213721(n))) = n, where pi(n) is the prime counting function.

Examples

			a(11) = 2 because prime(11) = 31 = 2*1 + 4 + 25 = 4 + 3*9.
		

Links

• Arkadiusz Wesolowski, Table of n, a(n) for n = 1..1000
• Index entries for sequences related to sums of squares

Crossrefs

Cf. A025428, A213721.

Programs

Mathematica

Table[Count[PowersRepresentations[Prime[n], 4, 2], _?(Min[#] > 0 &)], {n, 84}]