1,4

a(n) = number of 4k+3 primes (A002145) among primes in range 2 .. A000040(n).

Antti Karttunen, Table of n, a(n) for n = 1..65537

Other identities. For all n >= 1:

a(A080148(n)) = n.

a(n) + A267097(n) = n-1.

Accumulate[Table[If[IntegerQ[(n-3)/4], 1, 0], {n, Prime[Range[90]]}]] (* Harvey P. Dale, Mar 07 2018 *)

(Scheme, with Antti Karttunen's IntSeq-library)

(define A267098 (LEFTINV-LEASTMONO 1 1 A080148))

Cf. A000040, A002145, A080148, A267097.

Cf. also A267101.

Sequence in context: A245710 A137512 A157943 * A304110 A051134 A037458

Adjacent sequences: A267095 A267096 A267097 * A267099 A267100 A267101

nonn

Antti Karttunen, Feb 01 2016

approved