A172488 - OEIS

%I #3 Jun 03 2011 03:17:29

%S 12289,18433,139969,209953,472393

%N Primes of the form 2^i * 3^j + 1 with i + j = 13

%C Note that bases 2 = prime(1), 3 = prime(2)

%C 13 = prime(prime(1) * prime(2))

%C A finite "FUN" sequence with 5 = prime(3) terms

%D E. I. Ignatjew, Mathematische Spielereien, Urania Verlag Leipzig/Jena/Berlin 1982

%D Helmut Kracke, Mathe-musische Knobelisken, Duemmler Bonn, 2. Auflage 1983

%e 12289 = 2^12 * 3^1 + 1 = prime(1470) = prime(2 * 3 * 5 * 7^2)

%e 18433 = 2^11 * 3^2 + 1 = prime(2111), index is prime(318)

%e 139969 = 2^6 * 3^7 + 1 = prime(13006), larger of a Prime Twin Couple: PTC(1608)

%e 209953 = 2^5 * 3^8 + 1 = prime(18802)

%e 472393 = 2^3 * 3^10 + 1 = prime(39420)

%Y A172315, A005105

%K fini,full,nonn

%O 1,1

%A Eva-Maria Zschorn (e-m.zschorn(AT)zaschendorf.km3.de), Feb 05 2010