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 A179975 Smallest k such that k*10^n is a sum of two successive primes. 11
 5, 3, 1, 6, 6, 6, 14, 6, 9, 19, 21, 21, 42, 93, 21, 6, 11, 2, 12, 111, 37, 39, 63, 38, 42, 24, 15, 15, 60, 6, 39, 82, 47, 58, 337, 49, 72, 25, 34, 21, 6, 107, 128, 96, 20, 2, 63, 231, 70, 7, 62, 144, 28, 151, 157, 33, 98, 55, 134, 162, 87, 201, 124, 303, 64, 106, 130, 13, 43 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS From Robert G. Wilson v, Aug 11 2010: (Start) A179975 n's such that a(n)=1: 3, 335, ..., . A179975 First occurrence of k: 3, 18, 2, ???, 1, 4, 50, 162, 9, 335, 17, 19, 68, 7, 27, ..., . Records: 5, 6, 14, 19, 21, 42, 93, 111, 337, 449, 862, 1049, 1062, 1122, 1280, 2278, 3168, 4290, ..., . (End) LINKS Robert G. Wilson v, Table of n, a(n) for n = 0..400. Dario Alejandro Alpern, Brilliant numbers [From Robert G. Wilson v, Aug 11 2010] EXAMPLE a(0)=5 because 5=2+3 a(1)=3 because 30=13+17 a(2)=1 because 100=47+53 a(3)=6 because 6000=2999+3001. MATHEMATICA Join[{5, 3}, Reap[Do[Do[n=10^m k; If[n==PreviousPrime[n/2]+NextPrime[n/2], Sow[k]; Break[]], {k, 2000}], {m, 2, 50}]][[2, 1]]] f[n_] := Block[{k = 1, tn = 10^n}, While[h = k*tn/2; NextPrime[h, -1] + NextPrime@h != k*tn, k++ ]; k]; f[1] = 3; Array[f, 70, 0] (* Robert G. Wilson v, Aug 11 2010 *) CROSSREFS Cf. A064397, A071220, A074924, A074925. Cf. A033873, A033874, A005235, A055211, A038804, A084475. - Robert G. Wilson v, Aug 11 2010 Sequence in context: A023578 A111487 A011505 * A019926 A249538 A322932 Adjacent sequences:  A179972 A179973 A179974 * A179976 A179977 A179978 KEYWORD nonn AUTHOR Zak Seidov, Aug 04 2010 EXTENSIONS More terms from Robert G. Wilson v, Aug 11 2010 STATUS approved

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Last modified May 25 12:30 EDT 2019. Contains 323568 sequences. (Running on oeis4.)