login
A267098
a(n) = number of 4k+3 primes among first n primes; least monotonic left inverse of A080148.
9
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
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. also A267101.
Sequence in context: A245710 A137512 A157943 * A304110 A051134 A347777
KEYWORD
nonn
AUTHOR
Antti Karttunen, Feb 01 2016
STATUS
approved