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 A103797 Indices of n such that A019565(n)-1 is prime. 2
 2, 3, 7, 9, 11, 21, 27, 29, 31, 39, 41, 47, 51, 53, 55, 61, 63, 67, 71, 81, 89, 91, 107, 113, 121, 123, 129, 131, 135, 139, 143, 149, 151, 157, 159, 163, 169, 175, 179, 183, 187, 191, 197, 199, 207, 211, 217, 223, 235, 241, 251, 259, 261, 269, 279, 281, 287, 295 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 LINKS EXAMPLE A019565(0)=1, 1-1=0 is not prime; A019565(1)=2, 2-1=1 is not prime; A019565(2)=3, 3-1=2 is prime, so a(1)=2. MATHEMATICA A019565 = Function[tn, k1 = tn; o = 1; tt = 1; While[k1 > 0, k2 = Mod[k1, 2]; If[k2 == 1, tt = tt*Prime[o]]; k1 = (k1 - k2)/2; o = o + 1]; tt]; Do[cp = A019565[n] - 1; If[PrimeQ[cp], Print[n]], {n, 0, 1000}] CROSSREFS Cf. A019565, A103796. Sequence in context: A280110 A203234 A212985 * A262814 A328982 A260641 Adjacent sequences:  A103794 A103795 A103796 * A103798 A103799 A103800 KEYWORD nonn AUTHOR Lei Zhou, Feb 22 2005 STATUS approved

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Last modified December 9 00:32 EST 2019. Contains 329871 sequences. (Running on oeis4.)