A366167 - OEIS

%I #17 Oct 09 2023 11:05:35

%S 25,146,201,221,249,302,365,529,662,681,849,949,1211,1282,1318,1343,

%T 1849,2517,3223,3398,3466,3635,3867,3949,4063,4749,4819,4997,5158,

%U 6049,6614,7023,7041,7066,7117,7921,8314,8471,8709,8727,8914,8981,9155,9235,9299,9563,10741,10895,10958,11435,11962

%N Semiprimes that are the sum of two successive terms of A092192.

%H Robert Israel, <a href="/A366167/b366167.txt">Table of n, a(n) for n = 1..10000</a>

%e a(3) = 201 is a term because 201 = 95 + 106 = A092192(7) + A092192(8).

%p SP:= select(t -> numtheory:-bigomega(t) = 2, [$1..10000]):

%p A092192:= select(t -> numtheory:-bigomega(t) = 2, SP[2..-1]+SP[1..-2]):

%p select(t -> numtheory:-bigomega(t) = 2, A092192[2..-1]+A092192[1..-2]);

%t sim = Select[Range[4, 100000], 2 == PrimeOmega[#];&]; se = Select[Drop[sim, 1]

%t + Drop[sim, -1], 2 == PrimeOmega[#] &];    Select[Drop[se, 1] + Drop[se, -1], 2

%t == PrimeOmega[#] &]

%o (PARI) upto(n) = {my(pr = 10, res = List(), semiprimes = List([4,6])); forfactored(i = 9, n, if(bigomega(i[2]) == 2, listpop(semiprimes, 1); listput(semiprimes, i[1]); s = semiprimes[1] + semiprimes[2]; if(bigomega(s) == 2, c = s + pr; if(c > n, return(res)); if(bigomega(c) == 2, listput(res, c)); pr = s))); res} \\ _David A. Corneth_, Oct 02 2023

%Y Cf. A001358, A092192.

%K nonn

%O 1,1

%A _Zak Seidov_ and _Robert Israel_, Oct 02 2023