|
| |
|
|
A070802
|
|
a(n)=prevprime[sigma(n)]-nextprime[phi(n)]=A070801(n)-A070800(n).
|
|
0
| |
|
|
1, 0, 4, 0, 8, 0, 8, 6, 12, 0, 18, 0, 16, 12, 20, 0, 30, 0, 30, 18, 20, 0, 48, 8, 28, 18, 40, 0, 60, 0, 44, 24, 36, 18, 76, 0, 40, 24, 72, 0, 76, 0, 60, 44, 48, 0, 96, 10, 66, 34, 68, 0, 94, 30, 84, 42, 60, 0, 150, 0, 58, 66, 90, 30, 116, 0, 76, 42, 110, 0, 164, 0, 76, 72, 102, 28
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 2,3
|
|
|
FORMULA
| a(n)=p[Pi(sigma[n])]-p[1+Pi(phi[n])]
|
|
|
EXAMPLE
| n=100:sigma[100]=217,prevprime[217]=211, phi[100]=40,nextprime[40]=41,a(100)=211-41=170. The difference is 0 for odd primes.
|
|
|
MATHEMATICA
| Table[Prime[PrimePi[DivisorSigma[1, w]]]- Prime[1+PrimePi[EulerPhi[w]]], {w, 2, 128}]
|
|
|
CROSSREFS
| Cf. A007917, A007818, A000010, A000203, A000720, A000040, A070800, A070801.
Sequence in context: A019111 A103554 A076261 * A114401 A073467 A021249
Adjacent sequences: A070799 A070800 A070801 * A070803 A070804 A070805
|
|
|
KEYWORD
| easy,nonn
|
|
|
AUTHOR
| Labos E. (labos(AT)ana.sote.hu), May 08 2002
|
| |
|
|
