1,11

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

Arkadiusz Wesolowski, Table of n, a(n) for n = 1..1000

Index entries for sequences related to sums of squares

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

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

Cf. A025428, A213721.

Sequence in context: A307757 A215283 A066518 * A111165 A349812 A029321

Adjacent sequences: A218488 A218489 A218490 * A218492 A218493 A218494

nonn

Arkadiusz Wesolowski, Nov 02 2012

approved