[seqfan] Wanted: parents of lucky numbers
Neil Sloane
njas at research.att.com
Fri Mar 20 22:23:05 CET 1998
Lucky Numbers: I just read a very low-level article by Martin Gardner
(Mathematical Intelligencer, Spring 1997, but not
worth tracking down) about the lucky numbers,
A000959, which behave very like the prime numbers.
There are many related sequences that should be in the sequence
table, if anyone is interested in computing them:
- - twin lucky numbers (lower, upper, middle numbers)
- - increasing gaps between lucky numbers (lower, upper, size of gap)
- - number of ways to write 2n+1 as a product of lucky numbers
(all lucky numbers are odd; 1 is lucky but it should be
ignored in some of these sequences)
- - 7, 37, 237, ... Martin mentions
the conjecture that every lucky number appears at the tail of a larger
lucky number. this is the sequence starting at 7.
- - Number of ways to write 2n as a sum of 2 lucky numbers
(conjectured to be always > 0 )
(Oh, i may have that, A002850. But i don't think
i have any of the others mentioned.)
- - numbers both lucky and prime
- - palindromic lucky numbers
- - differences, second differences, etc of luckies
- - numbers both lucky and square
etc -- the possibilites are endless
Neil Sloane
[Olivier's remark: to avoid duplicating effort on this easy topic
you can for instance announce to the list which ones you are going
to compute.]
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