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

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A138180 Irregular triangle read by rows: row n consists of all numbers x such that x and x+1 are both prime(n)-smooth numbers. 3
1, 1, 2, 3, 8, 1, 2, 3, 4, 5, 8, 9, 15, 24, 80, 1, 2, 3, 4, 5, 6, 7, 8, 9, 14, 15, 20, 24, 27, 35, 48, 49, 63, 80, 125, 224, 2400, 4374, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 14, 15, 20, 21, 24, 27, 32, 35, 44, 48, 49, 54, 55, 63, 80, 98, 99, 120, 125, 175, 224, 242, 384, 440, 539 (list; graph; refs; listen; history; internal format)
OFFSET

1,3

COMMENTS

A number x is p-smooth if all prime factors of x are <= p. The length of row n is A002071(n). Row n begins with 1 and ends with A002072(n). Each term of row n-1 is in row n.

REFERENCES

See A002071.

LINKS

T. D. Noe, Rows n=1..10 of triangle, flattened

CROSSREFS

Cf. A085152, A085153.

Sequence in context: A131959 A202688 A021046 * A079585 A058485 A204907

Adjacent sequences:  A138177 A138178 A138179 * A138181 A138182 A138183

KEYWORD

nonn,tabf

AUTHOR

T. D. Noe (noe(AT)sspectra.com), Mar 04 2008

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 14 20:38 EST 2012. Contains 205663 sequences.