A178466 - OEIS

A178466

Primes prime(k) such that the concatenation prime(k+1)//prime(k) is also prime.

3, 47, 53, 61, 131, 173, 199, 211, 233, 257, 353, 523, 587, 607, 619, 647, 653, 751, 797, 971, 991, 997, 1103, 1123, 1231, 1381, 1553, 1777, 1913, 1973, 1987, 2297, 2333, 2341, 2399, 2677, 2861, 3049, 3191, 3259, 3607, 3637, 3761, 3989

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

OFFSET

1,1

COMMENTS

53, 211, 653, 997, ... are also in A088712.

The role of the two primes is swapped in comparison to A030459.

The result of the concatenation is in A088784.

LINKS

Table of n, a(n) for n=1..44.

FORMULA

a(n) = A151799(A088712(n)).

EXAMPLE

The prime 53 is in the sequence because the next prime is 59 and 5953 is a prime.

MAPLE

read("transforms") ;

for n from 1 to 600 do p := ithprime(n) ; q := nextprime(p) ; r := digcat2(q, p) ; if isprime(r) then printf("%d, ", p) ; end if; end do: # R. J. Mathar, Jan 27 2011

MATHEMATICA

Transpose[Select[Partition[Prime[Range[600]], 2, 1], PrimeQ[FromDigits[ Flatten[ IntegerDigits/@Reverse[#]]]]&]][[1]] (* Harvey P. Dale, Feb 02 2011 *)

CROSSREFS

Cf. A030459, A030460, A088712.

Sequence in context: A260882 A128109 A159246 * A227171 A055058 A139845

Adjacent sequences: A178463 A178464 A178465 * A178467 A178468 A178469

KEYWORD

nonn,base

AUTHOR

Carmine Suriano, Jan 27 2011

STATUS

approved