A131504 - OEIS

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A131504

Array read by antidiagonals: a(m,n) = m-th integer from among those positive integers which are coprime to (m*n).

1, 1, 3, 1, 3, 4, 1, 5, 7, 7, 1, 3, 4, 7, 6, 1, 3, 7, 11, 11, 17, 1, 5, 4, 7, 8, 17, 8, 1, 3, 7, 9, 11, 17, 15, 15, 1, 3, 4, 11, 6, 17, 11, 15, 13, 1, 5, 7, 9, 17, 19, 15, 23, 25, 23, 1, 3, 4, 7, 6, 17, 9, 15, 13, 23, 12, 1, 3, 11, 11, 11, 19, 23, 19, 25, 37, 23, 35, 1, 5, 4, 9, 8, 17, 8, 23, 16 (list; table; graph; refs; listen; history; internal format)

	OFFSET	`1,3`
	EXAMPLE	`For example:` `a(6,5) = 19 because the positive integers which are coprime to (5*6) are 1,7,11,13,17,19,23,29,... and the 6th of these is 19.` `Array begins:` `1, 3, 4, 7, 6,17, 8,15,13,23,12,35,14,...` `1, 3, 7, 7,11,17,15,15,25,23,23,35,27,...` `1, 5, 4,11, 8,17,11,23,13,37,17,35,20,...` `1, 3, 7, 7,11,17,15,15,25,23,23,35,27,...` `1, 3, 4, 9, 6,19, 9,19,16,23,14,43,17,...` `1, 5, 7,11,17,17,23,23,25,37,35,35,41,...` `1, 3, 4, 9, 6,19, 8,17,16,29,13,41,16,...` `1, 3, 7, 7,11,17,15,15,25,23,23,35,27,...` `1, 5, 4,11, 8,17,11,23,13,37,17,35,20,...` `1, 3,11, 9,11,19,19,19,31,23,29,43,33,...` `1, 3, 4, 7, 6,19, 8,17,14,27,12,37,15,...` `1, 5, 7,11,17,17,23,23,25,37,35,35,41,...`
	MAPLE	`A131504 := proc(n, m) local mn, a, k ; mn := m*n ; k := 1; for a from 1 do if gcd(a, mn) = 1 then if k = m then RETURN(a) ; fi ; k := k+1 ; fi ; od: end: for d from 1 to 14 do for m from 1 to d do printf("%d, ", A131504(d+1-m, m)) ; od: od: - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 26 2007`
	CROSSREFS	`Cf. A069213.` `Sequence in context: A064884 A093560 A173934 * A008311 A175721 A081772` `Adjacent sequences: A131501 A131502 A131503 * A131505 A131506 A131507`
	KEYWORD	`nonn,tabl`
	AUTHOR	`Leroy Quet Aug 13 2007`
	EXTENSIONS	`More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 26 2007`

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Last modified February 16 04:18 EST 2012. Contains 205860 sequences.