A084194 Even numbers n such that the sum of the digits is prime and the sum of the digits of n/2 is also prime.

14, 32, 50, 58, 76, 94, 98, 104, 122, 140, 148, 166, 184, 188, 212, 230, 238, 256, 274, 278, 292, 296, 302, 320, 328, 346, 364, 368, 382, 386, 410, 418, 436, 454, 458, 472, 476, 490, 494, 500, 508, 526, 544, 548, 562, 566, 580, 584

Offset

1,1

Comments

Sometimes n/2 is prime.

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

3+2=5 for n=32 and 1+6=7 for n/2=16;
5+8=13 for n=58 and 2+9=11 for n/2=29;
2+1+2=5 for n=212 and 1+0+6=7 for n/2=106;
2+5+6=13 for n=256 and 1+2+8=11 for n/2=128.

Maple

filter:= proc(n)
  isprime(convert(convert(n, base, 10), `+`)) and isprime(convert(convert(n/2, base, 10), `+`))
end proc:
select(filter, [seq(i, i=2..1000, 2)]); # Robert Israel, Sep 04 2019

Prog

(PARI) isok(n) = {if (n % 2, return (0)); dn = digits(n); dh = digits(n/2); isprime(sum(i=1, #dn, dn[i])) && isprime(sum(i=1, #dh, dh[i])); } \\ Michel Marcus, Aug 12 2013

Crossrefs

Cf. A084201.

Sequence in context: A101183 A101444 A222414 * A031109 A155819 A120711

Adjacent sequences: A084191 A084192 A084193 * A084195 A084196 A084197

Keyword

base,nonn

Author

Patrick Capelle, Jun 20 2003

Extensions

More terms from Michel Marcus, Aug 12 2013

Status

approved