A350233 Integers that are divisible by 5 and not by 4, and whose reverse is divisible by 4 and not by 5.

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

Table of n, a(n) for n=1..53.

Ana Rechtman, Décembre 2021, 3e défi, Images des Mathématiques, CNRS, 2021.

Example

25 is term since it is divisible by 5 and not by 4, while 52, it 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

Cf. A004086, A350232.

Subsequence of A008587.

Sequence in context: A020283 A350207 A211462 * A278855 A137186 A109676

Adjacent sequences: A350230 A350231 A350232 * A350234 A350235 A350236

Keyword

nonn,base

Author

Michel Marcus, Dec 21 2021

Status

approved