login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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. 3
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 (list; graph; refs; listen; history; text; internal format)
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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 29 21:32 EST 2021. Contains 349416 sequences. (Running on oeis4.)