A130975 a(n) = sum of numbers without digit 1 and with product of digits = n-th 7-smooth number.

0, 2, 3, 26, 5, 61, 7, 296, 42, 77, 942, 99, 88, 3264, 1108, 1098, 110, 13338, 55, 465, 1342, 2341, 35906, 132, 21869, 14806, 2807, 1375, 179141, 77, 1332, 16826, 17494, 45546, 1619, 394746, 3108, 376165, 1443, 192545, 5097, 53100, 49989, 2326191

Offset

1,2

Links

Klaus Brockhaus, Table of n, a(n) for n = 1..100

Example

First 7-smooth number is 1. Sum of numbers without digit 1 and with product of digits = 1 is 0 since there are no such numbers. Hence a(1) = 0.
Eighth 7-smooth number is 8, numbers without digit 1 and with product of digits = 8 are 8, 24, 42, 222. These sum to 296, hence a(8) = 296.
Eleventh 7-smooth number is 12, numbers without digit 1 and with product of digits = 12 are 26, 34, 43, 62, 223, 232, 322. These sum to 942, hence a(11) = 942.
Fifteenth 7-smooth number is 18, numbers without digit 1 and with product of digits = 18 are 29, 36, 63, 92, 233, 323, 332. These sum to 1108, hence a(15) = 1108.

Crossrefs

Cf. A002473 (7-smooth numbers), A084796 (concatenation of prime factors of n in decreasing order).

Sequence in context: A127231 A060371 A358390 * A002748 A056004 A032812

Adjacent sequences: A130972 A130973 A130974 * A130976 A130977 A130978

Keyword

nonn,base

Author

Philippe Lallouet (philip.lallouet(AT)wanadoo.fr), Aug 23 2007

Extensions

Edited, corrected and extended by Klaus Brockhaus, Aug 26 2007

Status

approved