id:A109824 - OEIS Search Results

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a(n) is the number of consecutive integers starting with n summing up to a semiprime.

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3, 3, 5, 1, 4, 1, 2, 4, 1, 1, 5, 2, 4, 1, 1, 2, 2, 3, 2, 4, 1, 1, 13, 2, 1, 1, 2, 2, 4, 3, 6, 2, 1, 1, 1, 3, 6, 1, 1, 3, 5, 2, 2, 7, 2, 1, 2, 6, 1, 4, 1, 3, 4, 6, 1, 7, 1, 1, 2, 2, 2, 1, 6, 2, 1, 2, 4, 4, 1, 2, 2, 2, 4, 1, 14, 6, 1, 3, 2, 2, 5, 1, 13, 2, 1, 1, 1, 2, 4, 14, 1, 2, 1, 1, 1, 3, 4, 4, 5, 2 (list; graph; listen)

	OFFSET	`1,1`
	FORMULA	`A109824(n) = A109823(n) - n + 1.`
	PROGRAM	`(PARI) {issemiprime(n) = local(f); f = factorint(n)[, 2]; sum(i = 1, length(f), f[i]) == 2}{a2(n) = local(s, m); s=n; m=n; while(!issemiprime(s), m++; s+=m); m-n+1}`
	CROSSREFS	`Cf. A109411, A109823.` `Sequence in context: A021753 A062563 A091931 this_sequence A011399 A079887 A131843` `Adjacent sequences: A109821 A109822 A109823 this_sequence A109825 A109826 A109827`
	KEYWORD	`nonn`
	AUTHOR	`Zak Seidov (zakseidov(AT)yahoo.com) & Max Alekseyev (maxale(AT)gmail.com), Jul 03 2005`

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.

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