A173980 a(n) is the smallest term m in A173978 for which A020639(2m-3) = prime(n), n > 1.

6, 19, 40, 106, 112, 265, 220, 427, 625, 730, 871, 1252, 1141, 1717, 2095, 2332, 2716, 2380, 3445, 6097, 4465, 4027, 6187, 6646, 6415, 7675, 6796, 7141, 15991, 8701, 9106, 12400, 12025, 11251, 12610, 14995, 14101, 16117, 16696, 16201, 21631, 19006, 22486, 21967

Offset

2,1

Links

Amiram Eldar, Table of n, a(n) for n = 2..1000

Vladimir Shevelev, Theorems on twin primes-dual case, arXiv:0912.4006 [math.GM], 2009-2014.

Mathematica

m = 50; v = Table[0, {m}]; lpf[n_] := FactorInteger[n][[1, 1]]; aQ[n_] := (! PrimeQ[2 n - 3] || ! PrimeQ[2 n - 1]) && lpf[2 n - 3] < lpf[2 n - 1]; c = 0; n = 1; While[c < m - 1, If[aQ[n], s = PrimePi[lpf[2 n - 3]]; If[s > 1 && s <= m && v[[s]] == 0, v[[s]] = n; c++]]; n++]; Rest[v] (* Amiram Eldar, Sep 12 2019 *)

Crossrefs

Cf. A020639, A173978, A173977, A173979.

Sequence in context: A273455 A273571 A273778 * A299281 A212684 A035495

Adjacent sequences: A173977 A173978 A173979 * A173981 A173982 A173983

Keyword

nonn

Author

Vladimir Shevelev, Mar 04 2010

Extensions

More terms from Amiram Eldar, Sep 12 2019

Status

approved