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A242423 Numbers in whose prime factorization the indices of primes do not sum to a triangular number. 4
3, 4, 7, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 20, 23, 24, 26, 31, 32, 33, 34, 35, 37, 38, 39, 41, 42, 43, 44, 45, 49, 50, 51, 52, 53, 54, 55, 56, 58, 59, 60, 61, 62, 63, 65, 66, 67, 68, 69, 70, 71, 72, 74, 75, 77, 78, 79, 80, 81, 82, 83, 84, 87, 88, 89, 90, 92, 93, 94, 95, 96, 97, 98, 99, 100 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers k such that A010054(A056239(k)) is zero, or equally, such that A002262(A056239(k)) is not zero.

These are numbers such that any iterations of A242424 started from them lead eventually to a cycle greater than one. Please see the comments and references at A242422.

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..27575

EXAMPLE

3 = p_2 is present, because 2 is not a triangular number.

4 = p_1 * p_1 is present, because 1+1 = 2 is not a triangular number.

PROG

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

(define A242423 (ZERO-POS 1 1 (COMPOSE A010054 A056239)))

CROSSREFS

Complement: A242422.

Cf. A215366, A242424, A000217, A002262, A010054, A056239.

Sequence in context: A138225 A114889 A174659 * A010444 A010398 A010435

Adjacent sequences:  A242420 A242421 A242422 * A242424 A242425 A242426

KEYWORD

nonn

AUTHOR

Antti Karttunen, May 16 2014

STATUS

approved

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Last modified November 29 06:32 EST 2021. Contains 349416 sequences. (Running on oeis4.)