A387304 a(n) is the least integer k such that 7^k begins with n!.

0, 0, 4, 14, 4, 361, 588457, 588458, 2002708, 1176915, 3631984, 55465324, 984533316, 6654250045, 333285732852, 1325096646826, 602916794573

Offset

0,3

Links

Table of n, a(n) for n=0..16.

Formula

a(n) = A018866(n!).

Example

a(4) = 4 because 7^4 = 2401 is the smallest power of 7 beginning with 4! = 24.

Mathematica

a[n_] := Module[{target = IntegerDigits[n!], k = 0}, While[UnsameQ[Take[IntegerDigits[7^k], Length@target], target], k++]; k];
Table[a[n], {n, 0, 6}]

Crossrefs

Cf. A000142, A018866, A374922, A374923, A386547.

Sequence in context: A375925 A156985 A138229 * A131702 A276826 A029661

Adjacent sequences: A387301 A387302 A387303 * A387305 A387306 A387307

Keyword

nonn,base,more

Author

Zhining Yang, Aug 25 2025

Status

approved