

A114057


Start of record gap in odd semiprimes A046315.


0



9, 25, 39, 95, 267, 2369, 6559, 8817, 13705, 15261, 21583, 35981, 66921, 113009, 340891, 783757, 872219, 3058853, 3586843, 5835191, 12345473, 108994623, 248706917, 268749691, 679956119, 709239621, 3648864859, 3790337723, 4171420481, 33955869693, 34279038379
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OFFSET

1,1


COMMENTS

3 of the first 5 values of record gaps in odd semiprimes are also record merits = [A046315(k+1)A046315(k)]/log(A046315(k)]/), namely: (15  9) / log(9) = 6.28770982; (111  95) / log(95) = 8.09010923; (287  267) / log(267) = 8.24228608. It is easy to prove that there are gaps of arbitrary length in even semiprimes (A100484); can we prove that there are gaps of arbitrary length in odd semiprimes (A046315) and in semiprimes (A001358)?
The record gaps have lengths 6, 8, 10, 16, 20, 22, 24, 26, 28, 32, 36, 38, 40, 44, 50, 52, 60, 64, 70, 74.  T. D. Noe, Feb 03 2006


LINKS

Table of n, a(n) for n=1..31.


FORMULA

{a(n)} = {A046315(k) such that A046315(k+1)A046315(k) is a record}.


EXAMPLE

a(1) = A046315(2)A046315(1) = 15  9 = 6.
a(2) = A046315(5)A046315(4) = 33  25 = 8.
a(3) = A046315(8)A046315(7) = 49  39 = 10.
a(4) = A046315(20)A046315(19) = 111  95 = 16.
a(5) = A046315(55)A046315(54) = 287  267 = 20.


MATHEMATICA

f[n_] := Block[{k = n + 2}, While[ Plus @@ Last /@ FactorInteger@k != 2, k += 2]; k]; lst = {}; d = 0; a = b = 9; Do[{a, b} = {b, f[a]}; If[b  a > d, d = b  a; AppendTo[lst, a]], {n, 10^8}]; lst (* Robert G. Wilson v *)


CROSSREFS

Cf. A001358, A046315, A065516, A085809, A100484, A114412, A114021.
Sequence in context: A147403 A241764 A044451 * A227518 A031036 A291259
Adjacent sequences: A114054 A114055 A114056 * A114058 A114059 A114060


KEYWORD

easy,nonn


AUTHOR

Jonathan Vos Post, Feb 02 2006


EXTENSIONS

More terms from Robert G. Wilson v and T. D. Noe, Feb 03 2006
a(23)a(28) from Donovan Johnson, Mar 14 2010
a(29)a(31) from Donovan Johnson, Oct 20 2012


STATUS

approved



