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 A122261 Characteristic function of numbers having only factors that are Pierpont primes. 5
 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 0, 1, 0, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 1, 0, 0, 1, 0, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 1, 1, 0, 0, 0, 1, 1, 1, 1, 0, 1, 0, 1, 0, 1, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Antti Karttunen, Table of n, a(n) for n = 1..12289 Eric Weisstein's World of Mathematics, Pierpont Prime FORMULA Multiplicative with a(p) = A065333(p-1), for p prime. a(n) = if n=1 then 0 else A122262(n) - A122262(n-1). a(A122260(n)) = 1. a(n) = A122255(n) for n < 25. EXAMPLE For n = 11 = 11^1, 11 is not a Pierpoint prime because 11-1 = 10 = 2*5 has a prime factor larger than 3, thus a(11) = 0. For n = 25 = 5^2, 5 is a Pierpoint prime as 5-1 = 4 = 2^2 does not have any prime factors larger than 3, thus a(25) = 1. MATHEMATICA Block[{nn = 105, s}, s = Select[Sort@ Flatten@ Table[2^i*3^j + 1, {i, 0, Log2@ nn}, {j, 0, Log[3, nn/2^i]}] , PrimeQ]; Table[Boole[n == 1] + Boole@ AllTrue[FactorInteger[n][[All, 1]], MemberQ[s, #] &], {n, nn}]] (* Michael De Vlieger, Aug 23 2017, after Robert G. Wilson v at A005109 *) PROG (PARI) A065333(n) = ((3^valuation(n, 3)< A065333(p-1), (factor(n)[, 1]))); \\ Antti Karttunen, Aug 22 2017 CROSSREFS Cf. A005109, A065333, A122255, A122262 (partial sums). Characteristic function of A122260. Sequence in context: A225595 A228813 A122255 * A014922 A014988 A015076 Adjacent sequences:  A122258 A122259 A122260 * A122262 A122263 A122264 KEYWORD nonn,mult AUTHOR Reinhard Zumkeller, Aug 29 2006 EXTENSIONS An unnecessary part removed from the formula and the Example section added by Antti Karttunen, Aug 22 2017 STATUS approved

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Last modified May 17 09:03 EDT 2021. Contains 343969 sequences. (Running on oeis4.)