A267097 a(n) = number of 4k+1 primes among first n primes; least monotonic left inverse of A080147.

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

Offset

1,6

Comments

a(n) = number of 4k+1 primes (A002144) 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(A080147(n)) = n.

a(n) + A267098(n) = n-1.

Prog

(Scheme, with Antti Karttunen's IntSeq-library)
(define A267097 (LEFTINV-LEASTMONO 1 1 A080147))

Crossrefs

Cf. A000040, A002144, A080147, A267098.

Cf. also A267101.

Sequence in context: A120565 A244989 A296021 * A194198 A189674 A156250

Adjacent sequences: A267094 A267095 A267096 * A267098 A267099 A267100

Keyword

nonn

Author

Antti Karttunen, Feb 01 2016

Status

approved