[seqfan] Re: Two neighboring digits sum up to a prime

[Hans Havermann]

Jonathan Post:

> New sequence S: a(n) = smallest integer not yet in S such that two
> neighboring digits of S sum up to a semiprime (4, 6, 9, or 10).

(4, 6, 9, 10, 14, or 15)

> 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.
>
> Starting with 0:
>
> 0, 4, 2, 7, 3,  then seems to get stuck?

{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, ...}