A365448 Array read by antidiagonals: row 1 is the semiprimes A001358; for m > 1, row m is the semiprimes that are the sum of two successive terms of row m-1.

4, 6, 10, 9, 15, 25, 10, 51, 146, 422, 14, 69, 201, 551, 973, 15, 77, 221, 667, 1858, 2831, 21, 85, 249, 1191, 89855, 312493, 127418369, 22, 95, 302, 1343, 110099, 2676567, 154171217

Offset: 1

Author

Zak Seidov and Robert Israel, Oct 03 2023

Keywords

• nonn
• tabl
• more

Examples

			The first 7 rows are
4, 6, 9, 10, 14, 15, 21, 22, 25, 26, ...
10, 15, 51, 69, 77, 85, 95, 106, 115, 134, ...
25, 146, 201, 221, 249, 302, 365, 529, 662, 681, ...
422, 551, 667, 1191, 1343, 2661, 6621, 11207, 13637, 14183, ...
973, 1858, 89855, 110099, 202394, 332377, 352147, 383507, 469231, 528923, ...
2831, 312493, 2676567, 3754285, 4027807, 9438362, 10568289, 20372991, 20590454, 21591014, ...
127418369, 154171217, 213938227, 242408953, 296917233, 325907227, 345235903, 367725381, ...
T(4,3) = 667 is a term because 667 = 23 * 29 is a semiprime and 667 = 392 + 365 where 302 = T(3,6) and 365 = T(3,7).
		

Crossrefs

Cf. A001358 (first row), A092192 (second row), A366167 (third row).

Programs

Maple

R[1]:= select(t -> numtheory:-bigomega(t) = 2, [$1..5*10^6]): M[1]:= nops(R[1]):
for i from 2 do
  R[i]:= select(t -> numtheory:-bigomega(t) = 2, R[i-1][1..M[i-1]-1] + R[i-1][2..M[i-1]]);
  M[i]:= nops(R[i]);
  if M[i] = 0 then break fi
od:
L:= NULL:
for k from 2 to 8 do
  L:= L, seq(R[i][k-i],i=1..k-1)
od:
L;