OFFSET
1,1
COMMENTS
It appears that, except for the first term a(1)=9, each term of this sequence is twice a prime.
Besides base 1, and bases b>=n (bases greater than or equal to the number itself), for which any number can be a Harshad number, these numbers are Harshad numbers in 3 other bases (where b=2..n-1): b1, b2, and b3, where b1 is n/2, b2 is n/2 + 1, b3 is n-1. Except for a(1)=9 that is a Harshad number in bases 3, 4 and 7. - Daniel Mondot, Apr 03 2016
LINKS
Daniel Mondot, Table of n, a(n) for n = 1..29865
EXAMPLE
9 is a Harshad number in bases 3, 4 and 7 (not following pattern);
14 is a Harshad number in bases 7, 8 and 13;
22 is a Harshad number in bases 11, 12 and 21;
38 is a Harshad number in bases 19, 20 and 37;
46 is a Harshad number in bases 23, 24 and 45;
58 is a Harshad number in bases 29, 30 and 57;
62 is a Harshad number in bases 31, 32 and 61;
74 is a Harshad number in bases 37, 38 and 73;
86 is a Harshad number in bases 43, 44 and 85;
94 is a Harshad number in bases 47, 48 and 93;
47 = 94/2, 48 = 94/2 + 1, 93 = 94 - 1. - Daniel Mondot, Apr 03 2016
CROSSREFS
KEYWORD
nonn,base
AUTHOR
John W. Layman, Nov 10 2004
STATUS
approved