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A309489
Numbers k such that the sum of digits in odd places is equal to the sum of digits in even places in k!.
1
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
KEYWORD
nonn,base
AUTHOR
Daniel Starodubtsev, Aug 04 2019
STATUS
approved