A063149 Composite numbers which in base 5 contain their largest proper factor as a substring.

25, 35, 55, 65, 85, 95, 115, 125, 145, 155, 175, 185, 205, 215, 235, 245, 265, 275, 295, 305, 325, 335, 355, 365, 385, 395, 415, 425, 445, 455, 475, 485, 505, 515, 535, 545, 565, 575, 595, 605, 625, 635, 655, 665, 685, 695, 715, 725, 745, 755, 775, 785, 805

Offset

1,1

Links

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

Formula

a(n) = 30*n-a(n-1) for n>1, a(1)=25. [Vincenzo Librandi, Aug 07 2010]

Mathematica

Do[ If[ !PrimeQ[ n ] && StringPosition[ ToString[ FromDigits[ IntegerDigits[ n, 5 ] ] ], ToString[ FromDigits[ IntegerDigits[ Divisors[ n ] [ [ -2 ] ], 5 ] ] ] ] != {}, Print[ n ] ], {n, 2, 1000} ]

Crossrefs

Cf. A062238.

Sequence in context: A348423 A276290 A173251 * A046423 A347612 A331808

Adjacent sequences: A063146 A063147 A063148 * A063150 A063151 A063152

Keyword

nonn,base,easy

Author

Robert G. Wilson v, Aug 08 2001

Status

approved