A371016 Centered square numbers which are semiprime.

25, 85, 145, 221, 265, 365, 481, 545, 685, 841, 1405, 1513, 1985, 2245, 2813, 2965, 3281, 3785, 3961, 4141, 4705, 5305, 5513, 5941, 6161, 6385, 6613, 7081, 7813, 8065, 8321, 9113, 9385, 10805, 11101, 11401, 11705, 12013, 12961, 13285, 13945, 16021, 17113, 17861, 19405, 22261, 23113, 24865

Offset

1,1

Comments

All terms are odd numbers.

Links

Table of n, a(n) for n=1..48.

Example

25 = 5 * 5 = (2 * 3 * 4) + 1.
85 = 5 * 17 = (2 * 6 * 7) + 1.
145 = 5 * 29 = (2 * 8 * 9) + 1.

Mathematica

Select[Table[2*n*(n + 1) + 1, {n, 0, 120}], PrimeOmega[#] == 2 &] (* Amiram Eldar, Mar 08 2024 *)

Crossrefs

Intersection of A001358 and A001844.

Sequence in context: A253053 A365249 A166080 * A081272 A318293 A027026

Adjacent sequences: A371013 A371014 A371015 * A371017 A371018 A371019

Keyword

nonn

Author

Massimo Kofler, Mar 08 2024

Status

approved