OFFSET
1,1
EXAMPLE
2 (greatest odd divisor of neighbor 1 is equal to 1 and greatest odd divisor of neighbor 3 is equal to 3);
3 (2 -> 1 and 4 -> 1),
4 (3 -> 3 and 5 -> 5),
5 (4 -> 1 and 6 -> 3),
7 (6 -> 3 and 8 -> 1),
8 (7 -> 7 and 9 -> 9),
9 (8 -> 1 and 10 -> 5), ...
MATHEMATICA
Select[Select[Range[0, 10000], PrimePowerQ], And@@(If[#==1, True, PrimePowerQ@#]&/@(Max@Select[Divisors@#, OddQ]&/@{#-1, #+1}))&] (* Giorgos Kalogeropoulos, Mar 31 2021 *)
PROG
(PARI) isp(m) = my(t=m>>valuation(m, 2)); isprimepower(t) || t==1;
is(k) = isprimepower(k) && isp(k-1) && isp(k+1); \\ Jinyuan Wang, Mar 27 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, Mar 24 2021
EXTENSIONS
Name corrected by Jon E. Schoenfield, Mar 24 2021
a(33)-a(42) from Jinyuan Wang, Mar 27 2021
a(43)-a(45) from Martin Ehrenstein, Apr 28 2021
STATUS
approved