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 A052020 Sum of digits of k is a prime proper factor of k. 7
 12, 20, 21, 30, 50, 70, 102, 110, 111, 120, 133, 140, 200, 201, 209, 210, 230, 247, 300, 308, 320, 322, 364, 407, 410, 476, 481, 500, 506, 511, 605, 629, 700, 704, 715, 782, 803, 832, 874, 902, 935, 1002, 1010, 1011, 1015, 1020, 1040, 1066, 1088, 1100, 1101 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS For each prime p there are infinitely many terms with sum of digits p. - Robert Israel, Feb 26 2017 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 MAPLE filter:= proc(n) local s; s:= convert(convert(n, base, 10), `+`); isprime(s) and (n mod s = 0) end proc: select(filter, [\$10..10^4]); # Robert Israel, Feb 26 2017 PROG (Python) from sympy import isprime def ok(n): sd = sum(map(int, str(n))) return 1 < sd < n and n%sd == 0 and isprime(sd) print([k for k in range(1102) if ok(k)]) # Michael S. Branicky, Dec 20 2021 CROSSREFS Cf. A052018, A052019, A052021, A052022, A007953, A005349, A028834. Sequence in context: A171795 A170806 A038528 * A075078 A050421 A307517 Adjacent sequences: A052017 A052018 A052019 * A052021 A052022 A052023 KEYWORD nonn,base,easy AUTHOR Patrick De Geest, Nov 15 1999 STATUS approved

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Last modified December 8 14:30 EST 2023. Contains 367679 sequences. (Running on oeis4.)