A320881 Numbers equal to a prime plus its digit sum.

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

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