A108635 - OEIS

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A108635

Semiprimes with property that digits are in nonincreasing order.

4, 6, 9, 10, 21, 22, 33, 51, 55, 62, 65, 74, 77, 82, 85, 86, 87, 91, 93, 94, 95, 111, 221, 321, 411, 422, 511, 533, 542, 543, 551, 553, 554, 611, 622, 633, 655, 662, 721, 731, 753, 755, 763, 766, 771, 831, 841, 842, 843, 851, 862, 865, 866, 871, 886, 921, 922

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Table of n, a(n) for n=1..57.

EXAMPLE

The semiprime 14 is missing because 4 > 1.

MATHEMATICA

Select[Range[1000], Plus@@Last/@FactorInteger[ # ]\[Equal]2&&OrderedQ[Reverse[IntegerDigits[ # ]]]&]

CROSSREFS

Cf. A108634.

Sequence in context: A287296 A275197 A118778 * A071964 A135257 A118697

Adjacent sequences: A108632 A108633 A108634 * A108636 A108637 A108638

KEYWORD

nonn,base,easy,less

AUTHOR

Zak Seidov, Jun 14 2005

STATUS

approved