A222975 Smallest member of sociable quadruples with signature: abundant, abundant, deficient, deficient.

1264460, 2115324, 2784580, 7169104, 18656380, 28158165, 81128632, 174277820, 498215416, 1236402232, 1799281330, 2387776550, 2717495235, 2879697304, 15837081520, 17616303220, 91411869465, 111375706442, 661126361272, 741158497112, 1045805730255, 1092162882824

Offset

1,1

Comments

Members of a sociable quadruple are usually listed in the order with which they appear in the corresponding aliquot sequence. Therefore, in a sociable quadruple the 1st member is abundant, and the 4th member is deficient. In all, we can get 4 possibilities, and a sociable quadruple can be (with A for abundant, and D for deficient) : AADD, ADDD, ADAD, AAAD. The numbers in these sequences have been voluntarily limited to 12 digits maximum, the current status of the exhaustive search (see Pedersen link).

Links

Amiram Eldar, Table of n, a(n) for n = 1..28

Jan Munch Pedersen, Known Sociable Numbers of order four, Tables of Aliquot Cycles.

Example

The first quadruple of this type is: 1264460, 1547860, 1727636, 1305184, that are respectively abundant, abundant, deficient, deficient.

Crossrefs

Cf. A090615, A222976, A222977, A222978.

Sequence in context: A292217 A072892 A090615 * A180624 A081430 A254026

Adjacent sequences: A222972 A222973 A222974 * A222976 A222977 A222978

Keyword

nonn

Author

Michel Marcus, Mar 11 2013

Extensions

a(21)-a(22) from Amiram Eldar, Apr 05 2024

Status

approved