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A387634 Indices k such that s(k) is a prime p, s(k-1) = 2*p, and s(k+1) = 3*p, where s = A386482.

%I A387634 #11 Sep 06 2025 15:43:48
%S A387634 5,11,24,31,57,76,236,479,1532,7652,82123,129791,274542,419569,
%T A387634 3367328,7002435,7690249,45355072
%N A387634 Indices k such that s(k) is a prime p, s(k-1) = 2*p, and s(k+1) = 3*p, where s = A386482.
%e A387634 Table of n, a(n), with a(n) = k, listing s(k) and its immediate neighbors:
%e A387634  n  a(n) = k     s(k-1)      s(k)     s(k+1)
%e A387634 --------------------------------------------
%e A387634  1         5         6         3          9
%e A387634  2        11        14         7         21
%e A387634  3        24        22        11         33
%e A387634  4        31        38        19         57
%e A387634  5        57        62        31         93
%e A387634  6        76        94        47        141
%e A387634  7       236       262       131        393
%e A387634  8       479       634       317        951
%e A387634  9      1532      1894       947       2841
%e A387634 10      7652      8654      4327      12981
%e A387634 11     82123     96182     48091     144273
%e A387634 12    129791    154474     77237     231711
%e A387634 13    274542    316978    158489     475467
%e A387634 14    419569    475466    237733     713199
%e A387634 15   3367328   3946174   1973087    5919261
%e A387634 16   7002435   6796442   3398221   10194663
%e A387634 17   7690249   8819038   4409519   13228557
%t A387634 s = Import["https://oeis.org/A386482/b386482.txt", "Data"][[All, -1]]; m = Length[s]; t = TakeWhile[Import["https://oeis.org/A387077/b387077.txt", "Data"][[All, -1]], # <= m &]; Select[t, #1 == 2 #2 && #3 == 3 #2 & @@ s[[# - 1 ;; # + 1]] &] ]
%Y A387634 Cf. A064413, A386482, A386483, A387072, A387076, A387077, A387522, A387523, A387524.
%K A387634 nonn,more,new
%O A387634 1,1
%A A387634 _Michael De Vlieger_, Sep 04 2025
%E A387634 a(18) from _Chai Wah Wu_, Sep 06 2025