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A078726 Fermat numbers 2^(2^n) + 1 with digits sorted in increasing order and zeros suppressed. 2
3, 5, 17, 257, 35567, 2244677999, 111344445566777789, 111222233333334444445666666777788899, 111111222223333333344444455555555566666666777777778888888999999999999 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

The 0, 1, 2, 3, 5 and 7 terms of this sequence are primes. Are there any more?

LINKS

Table of n, a(n) for n=0..8.

MATHEMATICA

Table[FromDigits[Sort[IntegerDigits[2^2^n+1]]/.(0->Nothing)], {n, 0, 10}] (* Harvey P. Dale, Apr 11 2021 *)

CROSSREFS

Cf. A000215.

Sequence in context: A260377 A056130 A273871 * A019434 A164307 A125045

Adjacent sequences:  A078723 A078724 A078725 * A078727 A078728 A078729

KEYWORD

base,nonn,nice,changed

AUTHOR

Jason Earls, Dec 20 2002

STATUS

approved

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Last modified April 16 03:59 EDT 2021. Contains 343030 sequences. (Running on oeis4.)