A267098 a(n) = number of 4k+3 primes among first n primes; least monotonic left inverse of A080148.

0, 1, 1, 2, 3, 3, 3, 4, 5, 5, 6, 6, 6, 7, 8, 8, 9, 9, 10, 11, 11, 12, 13, 13, 13, 13, 14, 15, 15, 15, 16, 17, 17, 18, 18, 19, 19, 20, 21, 21, 22, 22, 23, 23, 23, 24, 25, 26, 27, 27, 27, 28, 28, 29, 29, 30, 30, 31, 31, 31, 32, 32, 33, 34, 34, 34, 35, 35, 36, 36, 36, 37, 38, 38, 39, 40, 40, 40, 40, 40, 41, 41, 42

Offset

1,4

Comments

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

Links

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

Formula

Other identities. For all n >= 1:

a(A080148(n)) = n.

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

Mathematica

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

Prog

(Scheme, with Antti Karttunen's IntSeq-library)
(define A267098 (LEFTINV-LEASTMONO 1 1 A080148))

Crossrefs

Cf. A000040, A002145, A080148, A267097.

Cf. also A267101.

Sequence in context: A245710 A137512 A157943 * A304110 A051134 A347777

Adjacent sequences: A267095 A267096 A267097 * A267099 A267100 A267101

Keyword

nonn

Author

Antti Karttunen, Feb 01 2016

Status

approved