A172488 Primes of the form 2^i * 3^j + 1 with i + j = 13

12289, 18433, 139969, 209953, 472393

Offset

1,1

Comments

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

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

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

References

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

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

Links

Table of n, a(n) for n=1..5.

Example

12289 = 2^12 * 3^1 + 1 = prime(1470) = prime(2 * 3 * 5 * 7^2)
18433 = 2^11 * 3^2 + 1 = prime(2111), index is prime(318)
139969 = 2^6 * 3^7 + 1 = prime(13006), larger of a Prime Twin Couple: PTC(1608)
209953 = 2^5 * 3^8 + 1 = prime(18802)
472393 = 2^3 * 3^10 + 1 = prime(39420)

Crossrefs

A172315, A005105

Sequence in context: A140688 A137489 A233900 * A133860 A133861 A133862

Adjacent sequences: A172485 A172486 A172487 * A172489 A172490 A172491

Keyword

fini,full,nonn

Author

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

Status

approved