A309325 Numbers that are the sum of two successive palindromes.

1, 3, 5, 7, 9, 11, 13, 15, 17, 20, 33, 55, 77, 99, 121, 143, 165, 187, 200, 212, 232, 252, 272, 292, 312, 332, 352, 372, 393, 414, 434, 454, 474, 494, 514, 534, 554, 574, 595, 616, 636, 656, 676, 696, 716, 736, 756, 776, 797, 818, 838, 858, 878, 898, 918, 938, 958, 978

Offset: 1

Author

Ilya Gutkovskiy, Jul 23 2019

Keywords

• nonn
• base

Links

• Index entries for sequences related to palindromes

Crossrefs

Cf. A002113, A046489, A046497, A260255, A261906.

Programs

Mathematica

Total /@ Partition[Select[Range[0, 500], PalindromeQ], 2, 1]

Python

from itertools import chain, count, islice
def A309325_gen(): # generator of terms
    c = 0
    for a in chain.from_iterable(chain((int((s:=str(d))+s[-2::-1]) for d in range(10**l,10**(l+1))), (int((s:=str(d))+s[::-1]) for d in range(10**l,10**(l+1)))) for l in count(0)):
        yield c+(c:=a)
A309325_list = list(islice(A309325_gen(),20)) # Chai Wah Wu, Jun 23 2022

Formula

a(n) = A002113(n) + A002113(n+1).