A347335 Lexicographically earliest sequence of distinct nonnegative integers such that the sum of three consecutive terms is a palindrome in base 10.

0, 1, 2, 3, 4, 15, 14, 26, 37, 25, 39, 13, 36, 6, 24, 47, 17, 35, 49, 27, 12, 5, 16, 23, 38, 40, 10, 51, 50, 20, 7, 28, 9, 18, 61, 22, 48, 29, 11, 59, 31, 21, 69, 41, 71, 19, 81, 91, 30, 60, 101, 111, 70, 122, 80, 90, 32, 100, 110, 42, 120, 130, 53, 8, 141, 63, 58, 121, 33, 68, 131, 43

Offset

1,3

Links

Table of n, a(n) for n=1..72.

Example

a(1) + a(2) + a(3) = 0 + 1 + 2 = 3 (palindrome);
a(2) + a(3) + a(4) = 1 + 2 + 3 = 6 (palindrome);
a(3) + a(4) + a(5) = 2 + 3 + 4 = 9 (palindrome);
a(4) + a(5) + a(6) = 3 + 4 + 15 = 22 (palindrome); etc.

Prog

(Python)
def ispal(n): s = str(n); return s == s[::-1]
def aupton(terms):
    alst, seen = [0, 1], {0, 1}
    for n in range(2, terms):
        an, partial_sum = 1, sum(alst[-2:])
        while an in seen or not ispal(partial_sum + an): an += 1
        alst.append(an); seen.add(an)
    return alst
print(aupton(201)) # Michael S. Branicky, Aug 28 2021

Crossrefs

Cf. A228730.

Sequence in context: A251637 A365436 A035047 * A348672 A334619 A037323

Adjacent sequences: A347332 A347333 A347334 * A347336 A347337 A347338

Keyword

base,nonn

Author

Eric Angelini and Carole Dubois, Aug 28 2021

Status

approved