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A324988
Palindromes whose number of divisors is palindromic.
2
1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 22, 33, 44, 55, 66, 77, 88, 99, 101, 111, 121, 131, 141, 151, 161, 171, 181, 191, 202, 212, 222, 232, 242, 262, 282, 292, 303, 313, 323, 333, 343, 353, 363, 373, 383, 393, 404, 424, 434, 454, 474, 484, 494, 505, 515, 535, 545
OFFSET
1,2
COMMENTS
Numbers m such that m and A000005(m) = tau(m) are both in A002113.
EXAMPLE
Number of divisors of palindrome number 22 with divisors 1, 2, 11 and 22 is 4 (palindrome number).
MAPLE
ispali:= proc(n) local L; L:= convert(n, base, 10); L = ListTools:-Reverse(L) end proc:
select(t -> ispali(t) and ispali(numtheory:-tau(t)), [$1..10000]); # Robert Israel, Mar 26 2019
MATHEMATICA
Select[Range@ 600, And[PalindromeQ@ #, PalindromeQ@ DivisorSigma[0, #]] &] (* Michael De Vlieger, Mar 24 2019 *)
PROG
(Magma) [n: n in [1..1000] | Intseq(n, 10) eq Reverse(Intseq(n, 10)) and Intseq(NumberOfDivisors(n), 10) eq Reverse(Intseq(NumberOfDivisors(n), 10))]
(PARI) ispal(n) = my(d=digits(n)); Vecrev(d) == d;
isok(n) = ispal(n) && ispal(numdiv(n)); \\ Michel Marcus, Mar 23 2019
CROSSREFS
Similar sequences for functions sigma(m) and pod(m): A028986, A324989.
Includes A002385, A046328 and A046329.
Sequence in context: A227858 A335779 A240601 * A276354 A084982 A110785
KEYWORD
nonn,base
AUTHOR
Jaroslav Krizek, Mar 23 2019
STATUS
approved