A307587 Numbers k such that the determinant of the Vandermonde matrix of their digits is equal to phi(k), the Euler totient function of k.

1, 2, 190, 280, 480, 1073, 1674, 1736, 4850, 15867, 16230, 16302, 23715, 24056, 25064, 35712, 52976, 54730, 75184, 105342, 456382, 964325

Offset

1,2

Comments

Tested all the 8877691 numbers with distinct digits; no additional terms. - Giovanni Resta, Apr 16 2019

Links

Table of n, a(n) for n=1..22.

Example

     | 1  1   1  |
det  | 1  9   81 | = 72  = phi(190).
     | 1  0   0  |

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 phi(n)=det(vandermonde(c)) then print(n); fi; od; end: P(10^9);

Crossrefs

Cf. A000005, A307586.

Sequence in context: A252765 A172801 A318195 * A235680 A085937 A142890

Adjacent sequences: A307584 A307585 A307586 * A307588 A307589 A307590

Keyword

nonn,base,fini,full

Author

Paolo P. Lava, Apr 16 2019

Status

approved