A133960 Home primes whose homeliness is 3.

211, 223, 311, 337, 373, 389, 547, 571, 1123, 1153, 1319, 1931, 2237, 2311, 2341, 2371, 2557, 2719, 2797, 2953, 2971, 3167, 3181, 3191, 3257, 3313, 3329, 3347, 3449, 3457, 3461, 3463, 3517, 3541, 3547, 3557, 3571, 3643, 3701, 3709, 3727, 3733, 3739

Offset

1,1

Comments

Number of terms < 10^n: 0, 0, 8, 65, 437, 3233, 24579, ... .

Links

Table of n, a(n) for n=1..43.

Example

Only {4, 22, 211} -> 211, 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 = 3 - 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, A133959, A133956, A133957, A133958, A133962, A133964, A133966, A133968, A133970, A133972, A133974, A133976, A133978.

Sequence in context: A159911 A319141 A133959 * A031931 A246136 A087833

Adjacent sequences: A133957 A133958 A133959 * A133961 A133962 A133963

Keyword

nonn,base

Author

Robert G. Wilson v, Sep 30 2007

Status

approved