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

 

Logo

Annual Appeal: Today, Nov 11 2014, is the 4th anniversary of the launch of the new OEIS web site. 70,000 sequences have been added in these four years, all edited by volunteers. Please make a donation (tax deductible in the US) to help keep the OEIS running.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A069842 Number of distinct primes obtained by inserting a 1 at all possible places in n. This includes prefixing and suffixing. 9
1, 0, 2, 1, 0, 1, 2, 0, 1, 1, 0, 0, 2, 0, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 2, 1, 0, 0, 2, 0, 2, 0, 0, 0, 2, 0, 1, 1, 0, 1, 1, 0, 0, 1, 0, 0, 3, 0, 1, 1, 0, 1, 0, 0, 2, 0, 0, 1, 0, 0, 3, 1, 0, 1, 2, 0, 2, 1, 0, 0, 1, 0, 1, 1, 0, 0, 2, 0, 2, 1, 0, 0, 0, 0, 0, 1, 0, 0, 2, 0, 1, 1, 0, 0, 2, 0, 3, 0, 0, 1, 3, 0, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..105.

EXAMPLE

a(13) = 2 because 13 -> 113, 113, 131 -> 113 and 131 which are both prime.

MATHEMATICA

Table[ Count[ PrimeQ[ Union[ FromDigits /@ Table[ Insert[ IntegerDigits[n], 1, j], {j, 1, Floor[ Log[10, n] + 2]}]]], True], {n, 1, 105}]

CROSSREFS

Cf. A069843, A069844, A069845, A069846, A069847, A069848, A069849, A069850, A069851.

Sequence in context: A178651 A046810 A039999 * A083056 A244422 A061896

Adjacent sequences:  A069839 A069840 A069841 * A069843 A069844 A069845

KEYWORD

base,nonn

AUTHOR

Amarnath Murthy, Apr 16 2002

EXTENSIONS

More terms from Vladeta Jovovic, Apr 17 2002

Edited by Robert G. Wilson v, Apr 18 2002

STATUS

approved

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

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

Last modified November 27 01:09 EST 2014. Contains 250152 sequences.