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 A353530 Numbers k such that the smallest prime that does not divide them is of the form 4m+1. 3
 6, 12, 18, 24, 36, 42, 48, 54, 66, 72, 78, 84, 96, 102, 108, 114, 126, 132, 138, 144, 156, 162, 168, 174, 186, 192, 198, 204, 216, 222, 228, 234, 246, 252, 258, 264, 276, 282, 288, 294, 306, 312, 318, 324, 336, 342, 348, 354, 366, 372, 378, 384, 396, 402, 408, 414, 426, 432, 438, 444, 456, 462, 468, 474, 486, 492 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Numbers k such that A053669(k) is in A002144. The asymptotic density of this sequence is Sum_{p prime, p == 1 (mod 4)} ((p-1)/(Product_{q prime, q <= p} q)) = 0.1337642792... . - Amiram Eldar, Jul 25 2022 LINKS Table of n, a(n) for n=1..66. EXAMPLE The smallest prime that does not divide 6 = 2*3, is 5, which is of the form 4m+1, therefore 6 is included in this sequence. MATHEMATICA f[n_] := Module[{p = 2}, While[Divisible[n, p], p = NextPrime[p]]; p]; Select[Range[500], Mod[f[#], 4] == 1 &] (* Amiram Eldar, Jul 25 2022 *) PROG (PARI) A053669(n) = forprime(p=2, , if(n%p, return(p))); \\ From A053669 A353528(n) = (1==(A053669(n)%4)); isA353530(n) = A353528(n); CROSSREFS This is not equal to A342051 \ A005408. Cf. A353531 for a complement among the even numbers. Cf. A002144, A053669, A353526, A353528 (characteristic function). Sequence in context: A189781 A182302 A358757 * A244193 A329878 A215142 Adjacent sequences: A353527 A353528 A353529 * A353531 A353532 A353533 KEYWORD nonn AUTHOR Antti Karttunen, Apr 24 2022 STATUS approved

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Last modified July 24 12:40 EDT 2024. Contains 374583 sequences. (Running on oeis4.)