A133962 Home primes whose homeliness is 4.

379, 2347, 2383, 2389, 3331, 3359, 3373, 3719, 3767, 4397, 4759, 7331, 7457, 7523, 7547, 7823, 11251, 13883, 17137, 17317, 19157, 19181, 22367, 22397, 23131, 23173, 23197, 23311, 23593, 23677, 23767, 23911, 29101, 31063, 31123, 31181, 31189

Offset

1,1

Comments

Number of terms < 10^n: 0, 0, 1, 16, 146, 1085, 8522, ... .

Links

Table of n, a(n) for n=1..37.

Example

Only (42,74,237,379) -> 379, etc.

Mathematica

lst = {}; f[n_] := FromDigits@ Flatten[ IntegerDigits@ Table[ #[[1]], {#[[2]]}] & /@ FactorInteger@n, 2]; h[n_] := NestWhileList[f@# &, n, !PrimeQ@# &, 1, 28]; Do[p = h[n][[ -1]]; If[ PrimeQ@p && p < 10^7 && p != n, Print[{n, p}]; AppendTo[lst, p]], {n, 2, 1000}];
d = 4 - 2; lsu = {}; Do[ If[ lst[[n]] == lst[[n + d]] && lst[[n - 1]] != lst[[n]] && lst[[n]] != lst[[n + d + 1]], AppendTo[lsu, lst[[n]]]], {n, 188004 - d - 1}]; Take[Union@ lsu, 45]

Crossrefs

Cf. A037274, A118756, A133961, A133956, A133957, A133958, A133960, A133964, A133966, A133968, A133970, A133972, A133974, A133976, A133978.

Sequence in context: A142752 A271265 A133961 * A027503 A340200 A099728

Adjacent sequences: A133959 A133960 A133961 * A133963 A133964 A133965

Keyword

nonn,base

Author

Robert G. Wilson v, Sep 30 2007

Status

approved