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A226527 Slowest-growing sequence of 3-almost primes (trientprimes) where 1/(tp+1) sums to 1 without actually reaching it. 2
8, 12, 18, 20, 27, 28, 30, 42, 44, 45, 50, 52, 63, 66, 68, 70, 75, 76, 78, 92, 98, 99, 102, 105, 110, 114, 116, 117, 124, 125, 130, 138, 147, 148, 153, 154, 164, 165, 170, 171, 172, 174, 175, 182, 186, 188, 190, 195, 207, 212, 222, 230, 231, 236, 238, 242, 244, 245, 246, 255, 258, 261, 266, 268, 273, 275, 279, 282, 284, 285, 286, 290, 292, 310, 316, 318, 322, 325, 332, 333, 338, 343, 345, 354, 356, 357, 363, 366, 369, 370, 374, 385, 387, 388, 399, 402, 404, 406, 410, 412, 418, 423, 425, 426, 428, 429, 430, 434, 435, 436, 8662, 44335708, 1251938572491943, 1505273212784203338150808798466, 680617602541158152398258079780439819108542271775727566330763 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
See comments in A226526.
Deviates from A014612 after the 110th term.
LINKS
MATHEMATICA
kAlmostPrimeQ[n_, k_: 2] := Plus @@ Last /@ FactorInteger@ n == k (* For those who have Mmca v or later, you could use PrimeOmega@ n == k *) NextkAlmostPrime[n_, k_: 2, m_: 1] := Block[{c = 0, sgn = Sign[m]}, kap = n + sgn; While[c < Abs[m], While[ PrimeOmega[kap] != k, If[sgn < 0, kap--, kap++]]; If[ sgn < 0, kap--, kap++]; c++]; kap + If[sgn < 0, 1, -1]]; a[n_] := a[n] = Block[{sm = Sum[1/(a[i] + 1), {i, n - 1}]}, NextkAlmostPrime[ Max[a[n - 1], Floor[1/(1 - sm)]]]]; a[0] = 1; Do[ Print[{n, a[n] // Timing}], {n, 25}]
CROSSREFS
Sequence in context: A145784 A358763 A014612 * A212582 A046369 A066428
KEYWORD
nonn,hard
AUTHOR
STATUS
approved

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Last modified March 18 22:09 EDT 2024. Contains 370951 sequences. (Running on oeis4.)