A282090 Totient numbers (A002202) of the form 1 + k + k^2 + k^3 +...+ k^i (i > 1, k > 1).

40, 156, 400, 820, 1464, 2380, 3280, 3616, 3906, 5220, 7240, 9724, 12720, 19608, 20440, 25260, 30784, 37060, 60880, 66430, 70644, 81400, 93196, 97656, 106080, 120100, 135304, 151740, 169456, 177156, 188500, 254080, 265720, 278916, 333340, 363024, 394420, 427576, 462540, 499360

Offset

1,1

Comments

Totient numbers of the form (k^(i+1) - 1)/(k - 1) where k and i are both odd numbers that are greater than 1.

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Example

40 is a term because 1 + 3 + 9 + 27 = 40 is a totient number.

Prog

(PARI) list(lim)=my(v=List(), e, t); for(b=2, sqrt(lim), e=3; while((t=(b^e-1)/(b-1))<=lim, if(istotient(t), listput(v, t)); e++)); vecsort(Vec(v), , 8) \\ Ray Chandler, Feb 08 2017

Crossrefs

Intersection of A002202 and A053696.

Cf. A281962.

Sequence in context: A201233 A135848 A089548 * A250987 A300963 A146762

Adjacent sequences: A282087 A282088 A282089 * A282091 A282092 A282093

Keyword

nonn

Author

Altug Alkan, Feb 06 2017

Extensions

Terms confirmed by Ray Chandler, Feb 08 2017

Status

approved