A249729 Numbers not fixed by A250249 and A250250.

21, 27, 33, 39, 42, 45, 51, 54, 55, 57, 63, 65, 66, 69, 73, 75, 78, 81, 84, 85, 87, 90, 91, 93, 95, 99, 102, 103, 105, 108, 110, 111, 114, 115, 117, 119, 123, 125, 126, 129, 130, 132, 133, 135, 137, 138, 141, 145, 146, 150, 155, 156, 159, 161, 162, 165, 167, 168, 170, 171, 174, 175, 177, 180, 181, 182, 183, 185, 186, 187, 189, 190, 195, 197, 198, 201

Offset

1,1

Comments

Numbers for which A250249(n) <> n (equally: A250250(n) <> n).

If n is a member, then 2n is also a member. If any 2n is a member, then n is also a member. If n is a member, then the n-th prime, p_n (= A000040(n)) is also a member. If p_n is a member, then its index n is also a member. Thus the sequence is completely determined by its odd nonprime terms: 21, 27, 33, 39, 45, ..., and is obtained as a union of their multiples with powers of 2, and all prime recurrences that start with those values. For example, because 21 is present, then 2*21 = 42 is also present. Furthermore, 73 = p_21 is also present, as well as 367 = p_73 as well as 181 = p_42. See also comments at A250251 and A250249.

Links

Table of n, a(n) for n=1..76.

Prog

(Scheme, with Antti Karttunen's IntSeq-library)
(define A249729 (MATCHING-POS 1 1 (lambda (n) (not (= n (A250249 n))))))

Crossrefs

Complement: A250251.

Cf. A000040, A250249, A250250.

Sequence in context: A318544 A173836 A064507 * A280107 A264102 A364414

Adjacent sequences: A249726 A249727 A249728 * A249730 A249731 A249732

Keyword

nonn

Author

Antti Karttunen, Nov 18 2014

Status

approved