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A307586 Numbers k such that the determinant of the Vandermonde matrix of their digits is equal to sigma(k), the sum of divisors of k. 2
1, 1349, 12673, 12934, 16748, 16874, 17034, 28957, 60438, 67180, 80612, 81257, 87021, 93651, 413856, 712530, 813624, 942786 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Tested all the 8877691 numbers with distinct digits; no additional terms. - Giovanni Resta, Apr 16 2019
LINKS
EXAMPLE
| 1 1 1 1 1 |
| 1 2 4 8 16 |
det | 1 6 36 216 1296 | = 14400 = sigma(12673).
| 1 7 49 343 2401 |
| 1 3 9 27 81 |
MAPLE
with(numtheory): with(linalg): P:=proc(q) local a, c, k, n;
for n from 1 to q do a:=convert(n, base, 10): c:=[]:
for k from 1 to nops(a) do c:=[op(c), a[-k]]; od;
if sigma(n)=det(vandermonde(c)) then print(n); fi; od; end: P(10^9);
CROSSREFS
Sequence in context: A094037 A250088 A166193 * A224743 A260542 A307218
KEYWORD
nonn,base,fini,full
AUTHOR
Paolo P. Lava, Apr 16 2019
STATUS
approved

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Last modified February 24 05:58 EST 2024. Contains 370294 sequences. (Running on oeis4.)