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A104167 Numbers which when multiplied by any repunit prime Rp give a Smith number. 1
1540, 1720, 2170, 2440, 5590, 6040, 7930, 8344, 8470, 8920, 23590, 24490, 25228, 29080, 31528, 31780, 33544, 34390, 35380, 39970, 40870, 42490, 42598, 43480, 44380, 45955, 46270, 46810, 46990, 47908, 48790, 49960, 51490, 51625, 52345, 52570, 53290, 57070 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Numbers in the sequence must have a digital root of 1.
If the definition is modified, considering only repunits greater than 11, other numbers have the same property: 3304, 12070, 11080, 11620, 16030, 21340, 22330, 24130, 24220. - Mauro Fiorentini, Jul 16 2015
LINKS
S. S. Gupta, Smith Numbers.
Sham Oltikar, and Keith Wayland, Construction of Smith Numbers, Mathematics Magazine, vol. 56(1), 1983, pp. 36-37.
EXAMPLE
1720 is a number in the sequence because 1720*Rp is always a Smith number, where Rp is a Repunit prime. Let Rp=11, so 1720*11=18920, which is a Smith number as the sum of digits of 18920 is 1+8+9+2+0 = 20 and the sum of digits of prime factors of 18920 (i.e., 2*2*2*5*11*43) is also 20 (i.e., 2+2+2+5+1+1+4+3).
CROSSREFS
Sequence in context: A202166 A133354 A283900 * A237400 A200429 A092717
KEYWORD
base,nonn
AUTHOR
Shyam Sunder Gupta, Mar 10 2005
STATUS
approved

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Last modified February 21 03:46 EST 2024. Contains 370219 sequences. (Running on oeis4.)