A152080 - OEIS

A152080

Composite numbers c for which A000695(c) is prime.

55, 77, 87, 91, 115, 117, 121, 171, 185, 203, 213, 253, 299, 327, 329, 369, 405, 415, 425, 471, 475, 477, 481, 493, 501, 539, 583, 625, 637, 665, 675, 687, 721, 755, 789, 803, 805, 815, 817, 833, 835, 841, 855, 861, 913, 935, 955, 973, 979, 981

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Table of n, a(n) for n=1..50.

MATHEMATICA

f[n_] := FromDigits[IntegerDigits[n, 2], 4]; Select[Range[1000], CompositeQ[#] && PrimeQ[f[#]] &] (* Amiram Eldar, Dec 13 2018 *)

PROG

(PARI) a000695(n) = fromdigits(binary(n), 4);

lista(nn) = forcomposite(n=1, nn, if (isprime(a000695(n)), print1(n, ", "))); \\ Michel Marcus, Dec 13 2018

CROSSREFS

Cf. A000695, A077718, A152021, A152022, A152023, A152078, A152079.

Sequence in context: A217236 A050781 A060260 * A236769 A119224 A135984

Adjacent sequences: A152077 A152078 A152079 * A152081 A152082 A152083

KEYWORD

nonn

AUTHOR

Vladimir Shevelev, Nov 23 2008

EXTENSIONS

More terms derived from b000695.txt by Michel Marcus, Jun 02 2013

STATUS

approved