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A048537
a(n) is the smallest value of m such that A002378(m), the m-th oblong number, contains exactly n 4's.
10
6, 66, 215, 681, 6681, 12018, 201115, 1531159, 6541784, 21058215, 156340764, 675098840, 5868938806, 6666461193, 120186956049, 586862372693, 1115546688777, 4176295540840, 66589372231193, 66634408865198, 210842150539318, 2108185118566309, 21011769217380159, 185591342591574215, 67412496945629038
OFFSET
1,1
LINKS
Eric Weisstein's World of Mathematics, Pronic Number
EXAMPLE
From Jesse Sealand, Oct 06 2019: (Start)
a(1) = 6 since A002378(6) = 42;
a(2) = 66 since A002378(66) = 4422;
a(3) = 215 since A002378(215) = 46440;
a(4) = 681 since A002378(681) = 464442, etc.
(End).
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, May 15 1999
EXTENSIONS
a(13)-a(16) from Lars Blomberg, Jun 10 2011
Name edited by Jesse Sealand, Oct 06 2019
a(17) from Giovanni Resta, Oct 09 2019
a(18)-a(25) from Max Alekseyev, Jul 25 2024
STATUS
approved