A392496 2-rigid numbers. p-rigid numbers where p is prime are defined in A392499.

20, 70, 88, 104, 272, 304, 350, 368, 464, 572, 650, 836, 1184, 1312, 1376, 1504, 1696, 1888, 1952, 3770, 4030, 4288, 4544, 4672, 5056, 5312, 5696, 5704, 5810, 5830, 6208, 6464, 6592, 6790, 6808, 6848, 6976, 7144, 7192, 7232, 7630, 7910, 7912, 8024, 8056, 9272, 9590, 9730

Offset

1,1

Comments

Also the numbers that are sum-irreducible and abundant.

Links

Table of n, a(n) for n=1..48.

Peter Luschny, Composable, rigid, and sparse numbers. A Python notebook.

Prog

(Python) # Function 'is_rigid' is defined in A392499 (see also links).
def A392496_list(upto: int) -> list[int]:
    return [n for n in range(20, upto+1, 2) if 2 == is_rigid(n)]
print(A392496_list(9731))

Crossrefs

Cf. A005101 (abundant), A392650 (sum-irreducible), A006036, A392495 (p=3), A392499.

Sequence in context: A238101 A153728 A234367 * A071395 A362053 A357921

Adjacent sequences: A392493 A392494 A392495 * A392497 A392498 A392499

Keyword

nonn

Author

Peter Luschny, Jan 16 2026

Status

approved