|
Search: id:A080186
|
|
|
| A080186 |
|
Primes p such that 7 is the largest of all prime factors of the numbers between p and the next prime (cf. A052248). |
|
+0
2
|
|
| 13, 41, 419, 881, 1049, 2267, 2687, 3359, 3527, 5879, 6299, 7349, 7559, 8231, 8819, 10499, 18521, 26249, 26879, 28349, 29399, 30869, 33599, 35279, 49391, 81647, 100799, 102059, 131249, 131711, 134399, 158759, 170099, 183707, 197567, 241919
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
The sequence appears to consist of 13 and the lesser of twin primes q (A001359) such that q+1 is 7-smooth (A002473) but not 5-smooth (A051037, A080194).
|
|
EXAMPLE
|
13 is a term since 14 = 2*7, 15 = 3*5, 16 = 2^4 are the numbers between 13 and the next prime 17; 419 is a term since 420 = 2^2*3*5*7 is the only number between 419 and the next prime 421.
|
|
PROGRAM
|
(PARI) {forprime(p=2, 250000, q=nextprime(p+1); m=0; j=p+1; while(j<q&&m<=7, f=factor(j); a=f[matsize(f)[1], 1]; if(m<a, m=a); j++); if(m==7, print1(p, ", ")))}
|
|
CROSSREFS
|
Cf. A052248, A001359, A002473, A051037, A080194.
Adjacent sequences: A080183 A080184 A080185 this_sequence A080187 A080188 A080189
Sequence in context: A141970 A028468 A102130 this_sequence A116153 A116209 A002673
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Feb 10 2003
|
|
|
Search completed in 0.002 seconds
|
