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

%I

%S 0,2,3,26,5,61,7,296,42,77,942,99,88,3264,1108,1098,110,13338,55,465,

%T 1342,2341,35906,132,21869,14806,2807,1375,179141,77,1332,16826,17494,

%U 45546,1619,394746,3108,376165,1443,192545,5097,53100,49989,2326191

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

%H Klaus Brockhaus, <a href="/A130975/b130975.txt">Table of n, a(n) for n = 1..100</a>

%e 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.

%e 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.

%e 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.

%e 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.

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

%K nonn,base

%O 1,2

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

%E Edited, corrected and extended by _Klaus Brockhaus_, Aug 26 2007

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Last modified August 15 16:02 EDT 2020. Contains 336505 sequences. (Running on oeis4.)