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

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A060289 Number of distinct (non-overlapping) twin Harshad numbers whose sum is prime and where the 2nd Harshad is <= 10^n. 2
4, 5, 17, 53, 250, 1404, 9013 (list; graph; refs; listen; history; internal format)
OFFSET

0,1

FORMULA

Generate the twin Harshads whose sum is prime. Count how many there are where the 2nd Harshad in the pair is <= a consecutive power of 10.

EXAMPLE

a(0)=4 because there are four pairs of Harshads whose sum is prime and the 2nd Harshad in the pair is <=10; these are 1+2=3, 3+4=7, 5+6=11, 9+10=19. 8+9=17 is not included because this pair overlaps 7+8=15, which also happens to be not prime. (Another sequence might include such overlapping pairs.)

CROSSREFS

A060288, A005349, A060159.

Sequence in context: A061806 A119997 A010361 * A066879 A134750 A051949

Adjacent sequences:  A060286 A060287 A060288 * A060290 A060291 A060292

KEYWORD

easy,more,nonn,base

AUTHOR

Enoch Haga (Enokh(AT)comcast.net), Mar 23 2001

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Puzzles | Hot | Classics
Recent Additions | More pages | Superseeker | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement .

Last modified February 17 17:35 EST 2012. Contains 206061 sequences.