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 A358166 a(1) = 13; for n > 1, if a(n-1) is even, then a(n) = a(n-1)/2; otherwise, a(n) = a(n-1) + prime(a(n-1)). 1
 13, 54, 27, 130, 65, 378, 189, 1318, 659, 5592, 2796, 1398, 699, 5972, 2986, 1493, 13996, 6998, 3499, 36102, 18051, 218932, 109466, 54733, 730334, 365167, 5622764, 2811382, 1405691, 23685544, 11842772, 5921386, 2960693, 52246474, 26123237, 521463688, 260731844, 130365922, 65182961, 1364229390 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Does this sequence become cyclic? All the sequences defined the same as this one but with 1 <= a(1) <= 12 are known to become cyclic. a(81) = 1977693361846020549, so calculating a(82) will require calculating the 1977693361846020549th prime. LINKS Table of n, a(n) for n=1..40. EXAMPLE a(1) = 13 is odd, so a(2) = 13 + prime(13) = 13 + 41 = 54. a(2) = 54 is even, so a(3) = a(2)/2 = 54/2 = 27. a(3) = 27 is odd, so a(4) = 27 + prime(27) = 27 + 103 = 130, etc. MATHEMATICA NestList[If[EvenQ[#], #/2, # + Prime[#]] &, 13, 40] PROG (PARI) lista(nn) = my(va = vector(nn)); va[1] = 13; for (n=2, nn, if (va[n-1] % 2, va[n] = va[n-1] + prime(va[n-1]), va[n] = va[n-1]/2); ); va; \\ Michel Marcus, Nov 12 2022 CROSSREFS Cf. A293981, A350877, A014688. Sequence in context: A201486 A176617 A254895 * A195024 A071230 A027000 Adjacent sequences: A358163 A358164 A358165 * A358167 A358168 A358169 KEYWORD nonn,look,hard AUTHOR Sander G. Huisman, Nov 01 2022 STATUS approved

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Last modified October 2 18:16 EDT 2023. Contains 365840 sequences. (Running on oeis4.)