login
A084995
Numbers which can be written as the product of two different primes and the sum of digits is also prime.
1
14, 21, 34, 38, 58, 65, 74, 85, 94, 106, 111, 115, 119, 122, 133, 142, 146, 155, 166, 201, 203, 205, 209, 214, 218, 221, 247, 254, 265, 274, 278, 287, 298, 302, 319, 326, 335, 346, 355, 362, 371, 377, 382, 386, 391, 395, 403, 407, 427, 445, 454, 458, 469, 478, 481, 485
OFFSET
1,1
LINKS
FORMULA
Intersection of A028834 and A006881. - Andrew Howroyd, Jan 05 2020
EXAMPLE
E.g., 14 = 7*2 and 1+4 = 5 is also prime.
MATHEMATICA
Module[{nn=60}, Select[Union[Times@@@Subsets[Prime[Range[nn]], {2}]], PrimeQ[ Total[ IntegerDigits[#]]]&&#<=2Prime[nn]&]] (* Harvey P. Dale, Feb 28 2022 *)
PROG
(PARI) is(n)={bigomega(n)==2 && !issquare(n) && isprime(sumdigits(n))}
select(is, [1..500]) \\ Andrew Howroyd, Jan 05 2020
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Meenakshi Srikanth (menakan_s(AT)yahoo.com), Jun 30 2003
EXTENSIONS
Terms a(14) and beyond from Andrew Howroyd, Jan 05 2020
STATUS
approved