|
Search: id:A165198
|
|
|
| A165198 |
|
Primes from integers by taking the factorial of each digit and adding them up. |
|
+0
1
|
|
| 2, 2, 2, 3, 7, 3, 3, 7, 7, 3, 3, 3, 3, 5, 13, 31, 127, 727, 31, 127, 241, 727, 45361, 45361, 5, 5, 5, 5, 13, 31, 127, 727, 13, 31, 127, 727, 13, 13, 31, 31, 127, 127, 727, 727, 31, 31, 31, 31, 127, 241, 127, 241, 127, 127, 241, 241, 727, 727, 727, 727, 45361, 45361, 45361
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
The integers are considered in increasing order.
All primes eventually appear. Least integer k which produces the nth prime: 2, 12, 122, 13, 1223, 133, 12233, 1333, 122333, 1224, 134, 1334, 122334, 13334, 1223334, ..., . [From Robert G. Wilson v (rgwv(AT)rgwv.com), Sep 30 2009]
|
|
LINKS
|
Dario Alpern, Factorization using the Elliptic Curve Method
|
|
EXAMPLE
|
2 from 11 by 1! + 1!.
3 from 100 by 1! + 0! + 0!
13 from 133 by 1! + 3! + 3!
727 from 136 by 1! + 3! + 6!
45361 from 178 by 1! + 7! + 8!
155->241. 178->45361. 1223->11. 1224->29. 1333->19. 1334->37. 1336->733. 1345->151. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 17 2009]
|
|
MATHEMATICA
|
f[n_] := Plus @@ (IntegerDigits@ n!); k = 0; lst = {}; While[k < 783, a = f@k; If[ PrimeQ@a, AppendTo[lst, a]]; k++ ]; lst [From Robert G. Wilson v (rgwv(AT)rgwv.com), Sep 30 2009]
|
|
CROSSREFS
|
Cf. A061602. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 17 2009]
Sequence in context: A091712 A125721 A049798 this_sequence A024682 A091228 A134890
Adjacent sequences: A165195 A165196 A165197 this_sequence A165199 A165200 A165201
|
|
KEYWORD
|
base,nonn
|
|
AUTHOR
|
Parthasarathy Nambi (PachaNambi(AT)yahoo.com), Sep 07 2009
|
|
EXTENSIONS
|
Prepended 2!=2 and 10 -> 1!+0!=2. R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 17 2009
|
|
|
Search completed in 0.002 seconds
|
