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A131939 Least k such that the difference between consecutive 3-almost primes A014612(k) equals n, or 0 if no such k exists. 0
5, 3, 13, 1, 10, 2, 4, 31, 32, 36, 12, 7, 136, 19, 302, 486, 1094, 73, 1366, 6763, 1092, 2006, 8924, 4785, 18345, 18487, 42798, 16571, 11095, 57831, 60912, 4528, 24846, 41304, 232350, 233678, 123279, 1779265, 740729, 177385, 1015228, 1772286 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Index of smallest 3-almost prime gap equal to n. This is to 3-almost primes A014612 as A123375 is to semiprimes A001358. a(25) = 0 or a(25) > 10000. Conjecture: a(n) > 0 for all n.

LINKS

Table of n, a(n) for n=1..42.

FORMULA

a(n) = MIN{k such that A114403(k) = n, or 0 if no such k exists}. a(n) = MIN{k such that A014612(k+1) - A014612(k) = n, or 0 if no such k exists}.

EXAMPLE

a(1) = 5 because A014612(6)-A014612(5) = 28-27 = 1.

a(2) = 3 because A014612(4)-A014612(3) = 20-18 = 2.

a(3) = 13 because 66-63 = 3.

a(4) = 1 because 12-8 = 4.

a(5) = 10 because 50-45 = 5.

a(6) = 2 because 18-12 = 6.

a(7) = 4 because 27-20 = 7.

a(8) = 31 because 138-130 = 8.

a(9) = 32 because 147-138 = 9

a(10) = 36 because 164-154 = 10.

CROSSREFS

Cf. A014612, A114403, A123375.

Sequence in context: A245288 A104587 A300940 * A205522 A111744 A083781

Adjacent sequences:  A131936 A131937 A131938 * A131940 A131941 A131942

KEYWORD

nonn

AUTHOR

Jonathan Vos Post, Oct 05 2007

EXTENSIONS

More terms from R. J. Mathar, Oct 07 2007

STATUS

approved

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Last modified September 25 20:01 EDT 2020. Contains 337344 sequences. (Running on oeis4.)