A108655 Primes that are sums of the squares of two semiprimes.

97, 181, 241, 277, 421, 457, 541, 641, 661, 709, 757, 821, 1109, 1117, 1237, 1301, 1381, 1597, 1621, 1669, 1709, 1901, 2069, 2341, 2381, 2417, 2437, 2557, 2617, 2677, 2741, 2797, 3041, 3061, 3221, 3557, 3637, 3701, 3733, 3989, 4241, 4261, 4421, 4517

Offset

1,1

Comments

Subsequence of A002144.

a(n) = A074985(i) + A074985(j) for appropriate i and j.

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Example

A000040(733) = 5557 = 81 + 5476 = (3*3)^2 + (2*37)^2 =
A001358(3)^2 + A001358(25)^2 = A074985(3) + A074985(25),
therefore 5557 is a term.

Prog

(Haskell)
a108655 n = a108655_list !! (n-1)
a108655_list = filter f a000040_list where
   f p = any (> 0) $ map (a064911 . a037213 . (p -)) $
                         takeWhile (< p) a074985_list
-- Reinhard Zumkeller, Aug 09 2012

Crossrefs

Cf. A000404, A001358, A000290.

Sequence in context: A261376 A142094 A142212 * A107193 A256775 A364321

Adjacent sequences: A108652 A108653 A108654 * A108656 A108657 A108658

Keyword

nonn

Author

Reinhard Zumkeller, Jul 07 2005

Status

approved