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A350233
Integers that are divisible by 5 and not by 4, and whose reverse is divisible by 4 and not by 5.
1
25, 65, 210, 215, 230, 235, 250, 255, 270, 275, 290, 295, 405, 425, 445, 465, 485, 610, 615, 630, 635, 650, 655, 670, 675, 690, 695, 805, 825, 845, 865, 885, 2105, 2110, 2115, 2125, 2130, 2135, 2145, 2150, 2155, 2165, 2170, 2175, 2185, 2190, 2195, 2305, 2310, 2315, 2325, 2330, 2335
OFFSET
1,1
COMMENTS
Numbers beginning with 21, 23, 25, 27, 29, 40, 42, 44, 46, 48, 61, 63, 65, 67, 69, 80, 82, 84, 86, 88 and ending with 05, 10, 15, 25, 30, 35, 45, 50, 55, 65, 70, 75, 85, 90, 95. The number of d-digit terms is 3*10^(d-2) for d >= 3. - Jianing Song, Dec 24 2021
LINKS
Ana Rechtman, Décembre 2021, 3e défi, Images des Mathématiques, CNRS, 2021.
EXAMPLE
25 is a term since it is divisible by 5 and not by 4, while 52, its reverse, is divisible by 4 and not by 5.
MATHEMATICA
Select[5 * Range[500], ! Divisible[#, 4] && Divisible[(r = IntegerReverse[#]), 4] && ! Divisible[r, 5] &] (* Amiram Eldar, Dec 21 2021 *)
PROG
(PARI) isok(k) = if ((k%4) && !(k%5), k=fromdigits(Vecrev(digits(k))); (k%5) && !(k%4));
(Python)
from itertools import count, islice
def A350233gen(): return filter(lambda n:(m := int(str(n)[::-1])) % 5 and not m % 4, filter(lambda n: n % 4 and not n % 5, count(1)))
A350233_list = list(islice(A350233gen(), 20)) # Chai Wah Wu, Dec 21 2021
CROSSREFS
Subsequence of A008587.
Sequence in context: A020283 A350207 A211462 * A278855 A137186 A109676
KEYWORD
nonn,base,changed
AUTHOR
Michel Marcus, Dec 21 2021
STATUS
approved