A309489 Numbers k such that the sum of digits in odd places is equal to the sum of digits in even places in k!.

11, 18, 20, 25, 27, 28, 32, 35, 41, 43, 51, 57, 60, 68, 72, 74, 80, 102, 105, 107, 113, 121, 122, 138, 140, 145, 156, 161, 166, 171, 228, 233, 245, 282, 301, 307, 308, 311, 315, 329, 333, 335, 340, 347, 349, 351, 353, 366, 386, 412, 420, 454, 469, 478

Offset

1,1

Comments

Numbers k such that A000142(k) is a term of A135499. - Michel Marcus, Aug 04 2019

Links

Daniel Starodubtsev, Table of n, a(n) for n = 1..300

Mathematica

aQ[n_] := Total[(d = IntegerDigits[n!])[[1;; -1;; 2]]] == Total[d[[2;; -1;; 2]]]; Select[Range[500], aQ] (* Amiram Eldar, Aug 04 2019 *)

Prog

(PARI) isok(k) = {my(d = digits(k!), so=0, se=0); for (i=1, #d, if (i%2, so += d[i], se += d[i])); so == se; } \\ Michel Marcus, Aug 04 2019
(Python)
def c(n): s = str(n); return sum(map(int, s[::2])) == sum(map(int, s[1::2]))
def afind(limit):
    k, factk = 1, 1
    while k <= limit:
        if c(factk): print(k, end=", ")
        k += 1; factk *= k
afind(500) # Michael S. Branicky, Nov 18 2021

Crossrefs

Cf. A000142 (n!), A135499.

Sequence in context: A072967 A232658 A300062 * A054306 A093519 A031119

Adjacent sequences: A309486 A309487 A309488 * A309490 A309491 A309492

Keyword

nonn,base

Author

Daniel Starodubtsev, Aug 04 2019

Status

approved