|
Search: id:A129976
|
|
|
| A129976 |
|
Numbers n such that the numerator of Sum[n^k/k!, {k,0,n}] is a prime number. |
|
+0
1
|
|
| 1, 2, 3, 4, 5, 6, 8, 10, 14, 21, 33, 36, 56, 68, 94, 378, 1943, 2389, 5455
(list; graph; listen)
|
|
|
OFFSET
|
1,2
|
|
|
COMMENT
|
The corresponding primes are A120266(a(n)) = {2, 5, 13, 103, 1097, 1223, ...}
|
|
EXAMPLE
|
Sum[4^k/k!, {k,0,4}] = 103/3. The numerator is a prime, hence 4 is in the sequence.
|
|
MATHEMATICA
|
Do[ f=Numerator[Sum[n^k/k!, {k, 0, n}]]; If[PrimeQ[f], Print[{n, f}]], {n, 1, 378}]
|
|
CROSSREFS
|
Cf. A120266, A119029, A120267.
Sequence in context: A036415 A086736 A017846 this_sequence A105181 A096120 A050030
Adjacent sequences: A129973 A129974 A129975 this_sequence A129977 A129978 A129979
|
|
KEYWORD
|
hard,more,nonn
|
|
AUTHOR
|
Alexander Adamchuk (alex(AT)kolmogorov.com), Jun 13 2007
|
|
EXTENSIONS
|
Edited by Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Jul 22 2007
3 more terms from Ryan Propper (rpropper(AT)cs.stanford.edu), Jan 22 2008
|
|
|
Search completed in 0.002 seconds
|
