A084983 Palindromes made of only prime digits.

2, 3, 5, 7, 22, 33, 55, 77, 222, 232, 252, 272, 323, 333, 353, 373, 525, 535, 555, 575, 727, 737, 757, 777, 2222, 2332, 2552, 2772, 3223, 3333, 3553, 3773, 5225, 5335, 5555, 5775, 7227, 7337, 7557, 7777, 22222, 22322, 22522, 22722, 23232, 23332, 23532, 23732, 25252, 25352

Offset

1,1

Links

Andrew Howroyd, Table of n, a(n) for n = 1..1000

Mathematica

With[{p = Prime@ Range@ PrimePi@ 9}, Array[If[OddQ@ #1, Map[FromDigits@ Join[#, Reverse@ Most@ #] &, #2], Map[FromDigits@ Join[#, Reverse@ #] &, #2]] & @@ {#, Tuples[p, {Ceiling[#/2]}]} &, 5]] // Flatten (* Michael De Vlieger, Jan 28 2020 *)

Prog

(PARI) a(n)={my(k=4); while(n>2*k, n-=2*k; k*=4); my(v=[d*2+1+(!d)|d<-digits(k+n-1, 4)]); fromdigits(concat(v[2..#v-(n<=k)], Vecrev(v[2..#v])))} \\ Andrew Howroyd, Jan 27 2020

Crossrefs

Intersection of A002113 and A046034.

Sequence in context: A046034 A062087 A162457 * A062239 A066483 A114420

Adjacent sequences: A084980 A084981 A084982 * A084984 A084985 A084986

Keyword

nonn,base

Author

Meenakshi Srikanth (menakan_s(AT)yahoo.com), Jun 27 2003

Extensions

Terms a(33) and beyond from Andrew Howroyd, Jan 27 2020

Status

approved