A090635 Trajectory of 63 under the map k -> A003415(k) (taking the arithmetic derivative).

63, 51, 20, 24, 44, 48, 112, 240, 608, 1552, 3120, 8144, 16304, 32624, 65264, 130544, 264928, 678448, 1356912, 4979232, 19424016, 58272480, 226593936, 763164288, 3467499840, 16339520448, 65370077568, 295266178368, 1223245608192, 6931725175296, 40582548986112

Offset: 1

Author

N. J. A. Sloane, Dec 14 2003

Keywords

• nonn

References

• A. M. Gleason et al., The William Lowell Putnam Mathematical Competition: Problems and Solutions 1938-1964, Math. Assoc. America, 1980, p. 295.

Crossrefs

Cf. A003415, A090636, A090637.

Programs

PARI

A090635(n, a=63)={if(n<0, vector(-n, n, if(n>1, a=A003415(a), a)), for(n=2, n, a=A003415(a)); a)}  \\ For n<0 return the vector a[1..-n]. - M. F. Hasler, Nov 27 2019

Formula

a(n+1) = A003415(a(n)), a(1) = 63. a(n) = 4*A129286(n-3) for n > 2. - M. F. Hasler, Nov 27 2019

Extensions

More explicit name from M. F. Hasler, Nov 27 2019