

A061077


a(n) = sum of the products of the digits of the first n odd numbers.


1



1, 4, 9, 16, 25, 26, 29, 34, 41, 50, 52, 58, 68, 82, 100, 103, 112, 127, 148, 175, 179, 191, 211, 239, 275, 280, 295, 320, 355, 400, 406, 424, 454, 496, 550, 557, 578, 613, 662, 725, 733, 757, 797, 853, 925, 934, 961, 1006, 1069, 1150, 1150, 1150, 1150
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OFFSET

1,2


REFERENCES

Amarnath Murthy, Smarandache friendly numbers and a few more sequences, Smarandache Notions Journal, Vol. 12, No. 123, Spring 2001.


LINKS

Table of n, a(n) for n=1..53.


FORMULA

a(n) = Sum_{k = 1..n} product of the digits of 2k1.
a(5*10^n) = 25*46^n, so a(n) is roughly kn^1.662... where the exponent is log 46/log 10.  Charles R Greathouse IV, Sep 20 2012


EXAMPLE

a(7) = 1 + 3 + 5 + 7 + 9 + 1*1 + 1*3 = 29.


PROG

(PARI) pd(n) = my(d = digits(n)); prod(i=1, #d, d[i]);
a(n) = sum(k=1, n, pd(2*k1)); \\ Michel Marcus, Feb 01 2015


CROSSREFS

Cf. A061076, A061078.
Sequence in context: A225004 A074373 A067115 * A292675 A254719 A266918
Adjacent sequences: A061074 A061075 A061076 * A061078 A061079 A061080


KEYWORD

nonn,base,easy


AUTHOR

Amarnath Murthy, Apr 14 2001


EXTENSIONS

More terms from Matthew Conroy, Apr 16 2001
Offset corrected by Charles R Greathouse IV, Feb 01 2015


STATUS

approved



