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A182364 a(1) = 0; a(n) = smallest integer not yet in this sequence S such that two neighboring digits of S sum to a semiprime  (4, 6, 9, 10, 14, or 15). 0
0, 4, 2, 7, 3, 1, 5, 9, 6, 8, 13, 15, 18, 19, 51, 31, 33, 36, 37, 22, 24, 27, 28, 60, 40, 42, 45, 46, 81, 54, 55, 59, 63, 64, 68, 69, 131, 82, 72, 73, 77, 78, 133, 136, 86, 87, 222, 224, 227, 228, 137, 240, 90, 91, 95, 96, 313, 151, 315, 154, 242, 245, 155, 159, 181, 318, 182, 246, 319, 186, 331, 333, 187, 272, 273, 190, 404, 277, 278, 191, 336, 337, 281, 360, 406, 363, 195, 196, 364, 282, 286, 368, 287, 369, 513, 372, 409, 515, 422, 424, 518 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

This is to A001358 semiprimes. as Eric Angelini's “Smallest integer not yet in S such that two neighboring digits of S sum up to a prime”, is to A000040 Primes. Corrected and extended by Hans Havermann.

LINKS

Table of n, a(n) for n=1..101.

EXAMPLE

a(2) = 4 because 4 is the smallest integer k such that a(0) + k is a semiprime (2*2 = 4).

CROSSREFS

Cf. A001358.

Sequence in context: A076129 A010648 A198994 * A021238 A222622 A161179

Adjacent sequences:  A182361 A182362 A182363 * A182365 A182366 A182367

KEYWORD

nonn,base,easy

AUTHOR

Jonathan Vos Post, Apr 27 2012

STATUS

approved

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Last modified December 21 15:47 EST 2014. Contains 252324 sequences.