A282424 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

A282424

Semiprimes p such that next semiprime after p is p + 50.

1226777, 4732631, 5093729, 9210671, 12515461, 12917989, 16121409, 16183253, 16698881, 17263069, 19418903, 23003807, 24534161, 26519563, 26726659, 27625067, 29605299, 29772471, 32655031, 34027277, 34366179, 35340719, 37570683, 38117319, 38687461, 39038399, 39479381

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

All terms are odd because even semiprime 2*p plus 50 = 2*(p+25) is multiple of 4 and not semiprime.

Note that a(1) = 1226777 = A131109(50).

Smallest possible difference is 50 but among first 10000 terms

the least difference 100 is between a(325) = 228601303 and a(326) = 228601403.

LINKS

Zak Seidov, Table of n, a(n) for n = 1..10000

PROG

(PARI) lista(nn) = my(r); for(k=1, nn, if(bigomega(k)==2, if(k-r==50, print1(r, ", ")); r=k)); \\ Jinyuan Wang, May 23 2021