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 A320881 Numbers equal to a prime plus its digit sum. 2
 4, 6, 10, 13, 14, 17, 25, 28, 29, 35, 40, 46, 47, 50, 58, 61, 68, 73, 79, 80, 83, 94, 95, 103, 106, 107, 113, 115, 118, 119, 136, 137, 148, 152, 158, 163, 170, 173, 181, 184, 191, 196, 202, 206, 214, 215, 218, 230, 238, 241, 242, 248, 253, 259, 271, 274, 281, 286, 292, 293, 296, 307, 316 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Sequence A048520 lists the primes in this sequence. LINKS Table of n, a(n) for n=1..63. EXAMPLE a(1) = 4 = 2 + 2 = (the smallest prime, 2 = prime(1)) + (digit sum of 2). Similarly, a({2, 3, 5}) = 2*prime({2, 3, 4}), since the digit sum of single-digit primes is the prime itself. a(4) = 13 = 11 + (1 + 1) = A048520(1), the first prime in this sequence. a(6) = 17 = 13 + (1 + 3) = A048520(2), the second prime in this sequence. PROG (PARI) is_A320881(n)=select(p->p+sumdigits(p)==n, primes([n-9*#digits(n), n-2])) \\ Returns the list of all "solutions"; this has the boolean value of true iff the list is nonempty. - M. F. Hasler, Nov 08 2018 CROSSREFS Cf. A062028 (n + its digit sum), A047791 (A062028(n) is prime), A048519 (primes in A047791). Sequence in context: A177929 A086493 A234965 * A224796 A190370 A246439 Adjacent sequences: A320878 A320879 A320880 * A320882 A320883 A320884 KEYWORD nonn,base AUTHOR M. F. Hasler, Nov 08 2018 STATUS approved

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Last modified June 15 02:47 EDT 2024. Contains 373402 sequences. (Running on oeis4.)