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A236866 Positions of primes in A007775 (numbers not divisible by 2, 3 or 5). 1
2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 15, 16, 17, 18, 19, 20, 22, 23, 24, 26, 27, 28, 29, 30, 31, 34, 35, 37, 38, 40, 41, 42, 44, 45, 47, 48, 49, 51, 52, 53, 54, 57, 60, 61, 62, 63, 64, 65, 67, 69, 71, 72, 73, 74, 75, 76, 79, 82, 83, 84, 85, 89, 90, 93, 94, 95 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

From Antti Karttunen, Feb 01 2014: (Start)

Positions of primes among natural numbers coprime to 30.

Term 1 is missing from the sequence, because A007775(1)=1 is not considered a prime, terms 2 - 13 are all present, and 14 is the next term missing from here, as A007775(14)=49 is the first composite in that sequence.

(End)

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..10000

PROG

(Python)

import sympy

from sympy import isprime

i=0

for n in range(1000):

    if n%2 and n%3 and n%5:

        i+=1   # A007775(i)=n

        if isprime(n):  print str(i)+', ',

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

(define A236866 (MATCHING-POS 1 1 (lambda (n) (prime? (A007775 n)))))

;; Where a slow version of A007775 can be defined for example like this:

(define A007775 (MATCHING-POS 1 1 (lambda (n) (= 1 (gcd n 30)))))

;; from Antti Karttunen, Feb 01 2014

CROSSREFS

Cf. A007775, A181709.

Sequence in context: A004437 A298534 A291442 * A122526 A120401 A285356

Adjacent sequences:  A236863 A236864 A236865 * A236867 A236868 A236869

KEYWORD

nonn,easy

AUTHOR

Alex Ratushnyak, Jan 31 2014

STATUS

approved

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Last modified July 6 15:57 EDT 2022. Contains 355111 sequences. (Running on oeis4.)