A347401 Lexicographically earliest sequence of distinct terms > 0 such that the sum n + a(n) forms a palindrome in base 10.

1, 2, 3, 4, 6, 5, 15, 14, 13, 12, 11, 10, 9, 8, 7, 17, 16, 26, 25, 24, 23, 22, 21, 20, 19, 18, 28, 27, 37, 36, 35, 34, 33, 32, 31, 30, 29, 39, 38, 48, 47, 46, 45, 44, 43, 42, 41, 40, 50, 49, 60, 59, 58, 57, 56, 55, 54, 53, 52, 51, 70, 69, 68, 67, 66, 65, 64, 63, 62, 61, 80, 79, 78, 77, 76, 75, 74, 73

Offset

1,2

Links

Table of n, a(n) for n=1..78.

Example

For n = 4 we have a(4) = 4 and 4 + 4 = 8 is a palindrome in base 10;
for n = 5 we have a(5) = 6 and 5 + 6 = 11 is a palindrome in base 10;
for n = 6 we have a(6) = 5 and 6 + 5 = 11 is a palindrome in base 10;
for n = 7 we have a(7) = 15 and 7 + 15 = 22 is a palindrome in base 10;
for n = 8 we have a(8) = 14 and 8 + 14 = 22 is a palindrome in base 10; etc.

Prog

(Python)
def ispal(n): s = str(n); return s == s[::-1]
def aupton(terms):
    alst, seen = [1], {1}
    for n in range(2, terms+1):
        an = 1
        while an in seen or not ispal(n + an): an += 1
        alst.append(an); seen.add(an)
    return alst
print(aupton(200)) # Michael S. Branicky, Aug 30 2021

Crossrefs

Cf. A347335, A347336, A347400, A347402.

Sequence in context: A370740 A365536 A336038 * A361332 A240809 A214322

Adjacent sequences: A347398 A347399 A347400 * A347402 A347403 A347404

Keyword

base,nonn

Author

Eric Angelini and Carole Dubois, Aug 30 2021

Status

approved