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A267098 a(n) = number of 4k+3 primes among first n primes; least monotonic left inverse of A080148. 8
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 (list; graph; refs; listen; history; text; internal format)
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 A037458

Adjacent sequences:  A267095 A267096 A267097 * A267099 A267100 A267101

KEYWORD

nonn

AUTHOR

Antti Karttunen, Feb 01 2016

STATUS

approved

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Last modified May 28 03:59 EDT 2018. Contains 304733 sequences. (Running on oeis4.)