login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A039832 Numbers n such that n and n+1 both have 4 divisors. 7
14, 21, 26, 33, 34, 38, 57, 85, 86, 93, 94, 118, 122, 133, 141, 142, 145, 158, 177, 201, 202, 205, 213, 214, 217, 218, 253, 298, 301, 302, 326, 334, 381, 393, 394, 445, 446, 453, 481, 501, 514, 526, 537, 542, 553, 565, 622, 633, 634, 694, 697, 698, 706, 717, 745, 766, 778, 793, 802, 817 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

REFERENCES

D. Wells, Curious and interesting numbers, Penguin Books.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

EXAMPLE

14 and 15 both have 4 as number of divisors and are consecutive.

MATHEMATICA

Flatten[Position[Partition[Table[DivisorSigma[0, n], {n, 1000}], 2, 1], _?(#=={4, 4}&)]] (* Vincenzo Librandi, Oct 21 2012 *)

PROG

(PARI) isA039832(n) = numdiv(n)==4 && numdiv(n+1)==4 \\ Michael B. Porter, Feb 03 2010

CROSSREFS

Intersection of A005237 and A030513.

Cf. A038456, A039833.

Sequence in context: A274226 A324073 A006614 * A108633 A110478 A125967

Adjacent sequences:  A039829 A039830 A039831 * A039833 A039834 A039835

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Felice Russo, Olivier Gérard, Dec 11 1999

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified July 17 16:38 EDT 2019. Contains 325107 sequences. (Running on oeis4.)