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 A316476 Stable numbers. Numbers whose distinct prime indices are pairwise indivisible. 50
 1, 2, 3, 4, 5, 7, 8, 9, 11, 13, 15, 16, 17, 19, 23, 25, 27, 29, 31, 32, 33, 35, 37, 41, 43, 45, 47, 49, 51, 53, 55, 59, 61, 64, 67, 69, 71, 73, 75, 77, 79, 81, 83, 85, 89, 91, 93, 95, 97, 99, 101, 103, 107, 109, 113, 119, 121, 123, 125, 127, 128, 131, 135, 137 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS A prime index of n is a number m such that prime(m) divides n. LINKS Andrew Howroyd, Table of n, a(n) for n = 1..10000 EXAMPLE The prime indices of 45 are {2,2,3}, so the distinct prime indices are {2,3}, which are pairwise indivisible, so 45 belongs to the sequence. The prime indices of 105 are {2,3,4}, which are not pairwise indivisible (2 divides 4), so 105 does not belong to the sequence. MATHEMATICA Select[Range[100], Select[Tuples[If[#===1, {}, Cases[FactorInteger[#], {p_, k_}:>PrimePi[p]]], 2], UnsameQ@@#&&Divisible@@#&]=={}&] PROG (PARI) ok(n)={my(v=apply(primepi, factor(n)[, 1])); for(j=2, #v, for(i=1, j-1, if(v[j]%v[i]==0, return(0)))); 1} \\ Andrew Howroyd, Aug 26 2018 CROSSREFS Cf. A056239, A112798, A285572, A285573, A303362, A304713, A316468, A316475. Sequence in context: A115405 A257144 A328674 * A056867 A320324 A321698 Adjacent sequences:  A316473 A316474 A316475 * A316477 A316478 A316479 KEYWORD nonn AUTHOR Gus Wiseman, Jul 04 2018 STATUS approved

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Last modified August 14 18:32 EDT 2020. Contains 336483 sequences. (Running on oeis4.)