id:A116935 - OEIS Search Results

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Semiprimes (A001358) which are the concatenation of the numbers 1 through n for some n.

+0
3

123, 1234, 1234567, 12345678910111213141516171819202122232425262728293031323334 (list; graph; listen)

	OFFSET	`1,1`
	FORMULA	`{A007908} intersect {A001358}.`
	EXAMPLE	`a(1) = 123 = 3 * 41.` `a(2) = 1234 = 2 * 617.` `a(3) = 1234567 = 127 * 9721.` `a(4) = 2 * 6172839455055606570758085909601061116212631364146515661667.`
	CROSSREFS	`Cf. A001358, A007908.` `Sequence in context: A074303 A077379 A135475 this_sequence A103504 A115983 A167231` `Adjacent sequences: A116932 A116933 A116934 this_sequence A116936 A116937 A116938`
	KEYWORD	`base,nonn,less`
	AUTHOR	`Jonathan Vos Post (jvospost3(AT)gmail.com), Mar 20 2006`

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Last modified December 13 23:45 EST 2009. Contains 170824 sequences.