A083477 Smallest palindrome > 1 and == 1 (mod n-th palindrome).

2, 3, 4, 5, 6, 7, 8, 9, 55, 111, 111, 232, 353, 111, 595, 232, 353, 595, 10101, 1111, 606, 525, 424, 303, 323, 343, 363, 383, 10101, 10601, 1111, 929, 727, 505, 525, 545, 565, 585, 12121, 12521, 12921, 2332, 273372, 707, 727, 747, 767, 787, 10101, 12421

Offset

1,1

Links

Chai Wah Wu, Table of n, a(n) for n = 1..208

Example

a(11) = 111 because A002113(11) = 22 and 111 = 5*22+1.

Prog

(Python)
from itertools import count
def A083477(n):
    if n==1: return 2
    q =(c:=n+1-x)*x+int(str(c)[-2::-1] or 0) if n+1<(x:=10**(len(str(n+1>>1))-1))+(y:=10*x) else (c:=n+1-y)*y+int(str(c)[::-1] or 0)
    for k in count(n+2):
         if (p:=int((c:=k-x)*x+int(str(c)[-2::-1] or 0) if k<(x:=10**(len(str(k>>1))-1))+(y:=10*x) else (c:=k-y)*y+int(str(c)[::-1] or 0)))%q==1:
             return p # Chai Wah Wu, Jul 12 2024

Crossrefs

Cf. A083478.

Sequence in context: A087082 A122627 A122629 * A069510 A062388 A070244

Adjacent sequences: A083474 A083475 A083476 * A083478 A083479 A083480

Keyword

base,nonn,changed

Author

Amarnath Murthy and Meenakshi Srikanth (menakan_s(AT)yahoo.com), May 03 2003

Extensions

Corrected and extended by David Wasserman, Nov 16 2004

Status

approved