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A305887 The least increasing sequence of numbers where all pairwise sums are semiprimes, with a(1)=4. 0
4, 5, 10, 29, 173, 249, 19073, 71489, 1166789, 3800333, 7021253, 15920129, 84551600693 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All terms > 10 are congruent to {3, 9} mod 10.

Triangle of resulting semiprimes begins:

    9

   14,  15

   33,  34,  39

  177, 178, 183, 202

LINKS

Table of n, a(n) for n=1..13.

MATHEMATICA

Nest[Append[#, Block[{k = Last[#] + 1}, While[! AllTrue[#, PrimeOmega[k + #] == 2 &], k++]; k]] &, {4}, 7] (* Michael De Vlieger, Jun 14 2018 *)

CROSSREFS

Cf. A001358, A116656, A164979, A181620.

Sequence in context: A203853 A109675 A052508 * A074098 A196270 A295656

Adjacent sequences:  A305884 A305885 A305886 * A305888 A305889 A305890

KEYWORD

nonn,more

AUTHOR

Zak Seidov, Jun 14 2018

EXTENSIONS

a(13) from Giovanni Resta, Jun 14 2018

STATUS

approved

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Last modified May 29 03:06 EDT 2020. Contains 334696 sequences. (Running on oeis4.)