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A249730 Odd nonprime terms in A250251. 3
1, 9, 15, 25, 35, 49, 77, 121, 143, 147, 153, 169, 221, 289, 323, 361, 437, 529, 667, 841, 899, 961, 1147, 1369, 1517, 1681, 1763, 1849, 2021, 2209, 2491, 2809, 3127, 3481, 3599 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

This sequence gives the numbers which together with all their multiples with the powers of 2 give the starting values for the prime recurrences whose union is A250251, the fixed points of permutations A250249 and A250250.

After 1, contains the terms from columns 2 and 3 of Sieve of Eratosthenes: A083140 (A083221), but only from those rows r for which A055396(r) (the index of smallest dividing prime r) is fixed by A250249 and A250250, i.e. is in A250251. The first r for which this is not the case is 73, which is in A249729 instead. However, because there is an infinite number of primes in A250251 and especially, because 2 and 3 are among them, this sequence is infinite.

LINKS

Table of n, a(n) for n=1..35.

PROG

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

(define A249730 (MATCHING-POS 1 1 (lambda (n) (and (odd? n) (not (prime? n)) (= n (A250249 n))))))

CROSSREFS

Subsequence of A250251.

Cf. A083140, A083221, A249821, A250249, A250250.

Sequence in context: A227198 A279102 A319529 * A251415 A109888 A193227

Adjacent sequences:  A249727 A249728 A249729 * A249731 A249732 A249733

KEYWORD

nonn

AUTHOR

Antti Karttunen, Nov 18 2014

STATUS

approved

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Last modified April 6 11:51 EDT 2020. Contains 333273 sequences. (Running on oeis4.)