The On-Line Encyclopedia of Integer Sequences (OEIS)

The OEIS is supported by the many generous donors to the OEIS Foundation.

A137532 revision #8

A137532

a(n) = smallest positive integer k such that d(k) = d(k+n) = 2n, where d(m) (A000005) is the number of positive divisors of m, or 0 if no such k exists.

2, 6, 172, 66, 15952, 84, 22592, 888, 2196, 3750, 459932661

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

From Jacques Tramu, Apr 20 2008: (Start)

a(12) = ???

a(13) = 5547515219437003248294176693030899

a(17) = 1477350959671318879923111865392957430890479

a(19) > 7907^19 if it exists. (End)

LINKS

Table of n, a(n) for n=1..11.

PROG

(PARI) lq080419b(n, a)=n*=2; until(0, numdiv(a++)==n || next; numdiv(a+n\2)==n && break); a

for(i=1, 99, print1(lq080419b(i)", "))

CROSSREFS

Cf. A139416.

Sequence in context: A168649 A135937 A182523 * * A072116 A203430

Adjacent sequences: A137529 A137530 A137531 * A137533 A137534 A137535

KEYWORD

nonn,more

AUTHOR

M. F. Hasler, Apr 19 2008

EXTENSIONS

a(11) from Jacques Tramu, Apr 20 2008

STATUS

proposed