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 A122260 Multiplicative closure of Pierpont primes. 5
 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 24, 25, 26, 27, 28, 30, 32, 34, 35, 36, 37, 38, 39, 40, 42, 45, 48, 49, 50, 51, 52, 54, 56, 57, 60, 63, 64, 65, 68, 70, 72, 73, 74, 75, 76, 78, 80, 81, 84, 85, 90, 91, 95, 96, 97, 98, 100, 102, 104, 105, 108 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS If u and v are terms then also u*v is a term; A005109 is the generating subsequence; A122261(a(n)) = 1; A122254 is a subsequence: a(n) = A122254(n) = A048737(n) for n < 22. LINKS Ivan Neretin, Table of n, a(n) for n = 1..10000 Eric Weisstein's World of Mathematics, Pierpont Prime MATHEMATICA mx = 108; Select[Range@mx, Complement[FactorInteger[#][[All, 1]], Select[Prime@Range@mx, Max[FactorInteger[# - 1][[All, 1]]] < 5 &], {1}] == {} &] (* Ivan Neretin, Aug 13 2015 *) PROG (PARI) sm3(n)=n>>=valuation(n, 2); n==3^valuation(n, 3) is(n)=my(f=factor(n)[, 1]); for(i=1, #f, if(!sm3(f[i]), return(0))); 1 \\ Charles R Greathouse IV, Feb 21 2013 CROSSREFS Sequence in context: A031995 A023752 A048737 * A122254 A249626 A102823 Adjacent sequences:  A122257 A122258 A122259 * A122261 A122262 A122263 KEYWORD nonn AUTHOR Reinhard Zumkeller, Aug 29 2006 STATUS approved

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