|
| |
|
|
A072182
|
|
A Wallis pair (x,y) satisfies sigma(x^2) = sigma(y^2); sequence gives x's for Wallis pairs with x < y (ordered by values of x).
|
|
4
| |
|
|
4, 12, 28, 36, 44, 52, 68, 76, 84, 92, 108, 116, 124, 132, 148, 156, 164, 172, 188, 196, 204, 212, 228, 236, 244, 252, 268, 276, 284, 292, 308, 316, 324, 326, 332, 348, 356, 364, 372, 388, 396, 404, 406, 412, 428, 436, 444, 452, 468, 476, 484, 492, 508, 516
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,1
|
|
|
COMMENTS
| 4*A045572 is included in this sequence - Benoit Cloitre, Oct 22 2002
|
|
|
REFERENCES
| I. Kaplansky, The challenges of Fermat, Wallis and Ozanam (and several related challenges): II. Fermat's second challenge, Preprint, 2002.
|
|
|
EXAMPLE
| The first few pairs are all multiples of the first pair (4,5): (4, 5), (12, 15), (28, 35), (36, 45), (44, 55), (52, 65), ...
|
|
|
PROG
| (PARI) {w=[]; m=550; for(x=1, m, q=sigma(x^2); sq=sqrtint(q); for(y=x+1, sq, if(q==sigma(y^2), w=concat(w, [[x, y]])))); for(j=1, matsize(w)[2], print1(w[j][1], ", "))}
|
|
|
CROSSREFS
| Cf. A072186, A075768, A075769.
Sequence in context: A104384 A013697 A064444 * A009906 A194432 A194434
Adjacent sequences: A072179 A072180 A072181 * A072183 A072184 A072185
|
|
|
KEYWORD
| nonn,easy
|
|
|
AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Oct 19 2002
|
|
|
EXTENSIONS
| Extended by Klaus Brockhaus (klaus-brockhaus(AT)t-online.de) and Benoit Cloitre (benoit7848c(AT)orange.fr), Oct 22 2002
|
| |
|
|
