A108608 5-almost primes whose sum of factors is a prime.

48, 80, 108, 176, 252, 300, 368, 405, 420, 464, 468, 500, 567, 660, 675, 684, 848, 891, 944, 980, 1020, 1116, 1136, 1140, 1323, 1332, 1377, 1424, 1428, 1452, 1539, 1548, 1575, 1616, 1700, 1716, 1740, 1820, 1860, 1875, 1932, 2096, 2156, 2196, 2295, 2300

Offset

1,1

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Example

48=2*2*2*2*3 (5-almost prime) and 2+2+2+2+3=11 is a prime.

Mathematica

Select[Range[2500], PrimeOmega[#]==5&&PrimeQ[Total[Times@@@FactorInteger[#]]]&] (* Harvey P. Dale, Apr 07 2022 *)

Prog

(PARI) is(n)=my(f=factor(n)); sum(i=1, #f~, f[i, 2])==5 && isprime(sum(i=1, #f~, f[i, 1]*f[i, 2])) \\ Charles R Greathouse IV, Oct 11 2013

Crossrefs

Cf. A107707, A108607, A108609 (resp.) 3, 4, 6 (resp.)-almost primes whose sum of factors is a prime.

Sequence in context: A348527 A362969 A110229 * A030628 A178739 A261548

Adjacent sequences: A108605 A108606 A108607 * A108609 A108610 A108611

Keyword

nonn

Author

Zak Seidov, Jun 12 2005

Status

approved