

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
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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



