A382380 Greater of twin self numbers, i.e., larger member of the pair of self numbers differing by 2.

3, 5, 7, 9, 110, 211, 312, 413, 514, 615, 716, 817, 918, 1111, 1212, 1313, 1414, 1515, 1616, 1717, 1818, 1919, 2112, 2213, 2314, 2415, 2516, 2617, 2718, 2819, 2920, 3113, 3214, 3315, 3416, 3517, 3618, 3719, 3820, 3921, 4114, 4215, 4316, 4417, 4518, 4619, 4720, 4821, 4922, 5115, 5216, 5317, 5418

Offset: 1

Author

Shyam Sunder Gupta, Mar 23 2025

Keywords

• nonn
• base

Comments

The number of twin self-numbers up to 10^n (for n > 2) is 9 * 10^(n-3) + 4. This has been verified up to n = 10.

Links

• Shyam Sunder Gupta, Table of n, a(n) for n = 1..9004
• Shyam Sunder Gupta, On Some Marvellous Numbers of Kaprekar, Exploring the Beauty of Fascinating Numbers, Springer (2025) Ch. 9, 275-315.

Crossrefs

Cf. A003052, A374101.

Formula

a(n) = A374101(n) + 2.