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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.

%I A365448 #38 Jan 04 2024 21:12:52
%S A365448 4,6,10,9,15,25,10,51,146,422,14,69,201,551,973,15,77,221,667,1858,
%T A365448 2831,21,85,249,1191,89855,312493,127418369,22,95,302,1343,110099,
%U A365448 2676567,154171217
%N 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.
%e A365448 The first 7 rows are
%e A365448 4, 6, 9, 10, 14, 15, 21, 22, 25, 26, ...
%e A365448 10, 15, 51, 69, 77, 85, 95, 106, 115, 134, ...
%e A365448 25, 146, 201, 221, 249, 302, 365, 529, 662, 681, ...
%e A365448 422, 551, 667, 1191, 1343, 2661, 6621, 11207, 13637, 14183, ...
%e A365448 973, 1858, 89855, 110099, 202394, 332377, 352147, 383507, 469231, 528923, ...
%e A365448 2831, 312493, 2676567, 3754285, 4027807, 9438362, 10568289, 20372991, 20590454, 21591014, ...
%e A365448 127418369, 154171217, 213938227, 242408953, 296917233, 325907227, 345235903, 367725381, ...
%e A365448 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).
%p A365448 R[1]:= select(t -> numtheory:-bigomega(t) = 2, [$1..5*10^6]): M[1]:= nops(R[1]):
%p A365448 for i from 2 do
%p A365448   R[i]:= select(t -> numtheory:-bigomega(t) = 2, R[i-1][1..M[i-1]-1] + R[i-1][2..M[i-1]]);
%p A365448   M[i]:= nops(R[i]);
%p A365448   if M[i] = 0 then break fi
%p A365448 od:
%p A365448 L:= NULL:
%p A365448 for k from 2 to 8 do
%p A365448   L:= L, seq(R[i][k-i],i=1..k-1)
%p A365448 od:
%p A365448 L;
%Y A365448 Cf. A001358 (first row), A092192 (second row), A366167 (third row).
%K A365448 nonn,tabl,more
%O A365448 1,1
%A A365448 _Zak Seidov_ and _Robert Israel_, Oct 03 2023