login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A252670 a(n) is exponential digital index of prime(n). 1
22, 0, 11, 4, 2, 0, 0, 2, 1, 0, 0, 2, 2, 0, 0, 0, 0, 2, 0, 2, 2, 0, 0, 0, 0, 2, 0, 0, 2, 1, 2, 1, 0, 0, 0, 0, 0, 2, 0, 0, 1, 2, 0, 0, 0, 0, 2, 0, 0, 1, 0, 0, 3, 1, 0, 0, 0, 2, 0, 0, 0, 0, 2, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 1, 0, 1, 0, 0, 5, 0, 2, 0, 0, 1, 0, 0, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

For the definition of the exponential digital index of a prime p (EDI(p)), see comment in A252668.

Is 22 the maximal term? Is 11 the second maximal term?

LINKS

Table of n, a(n) for n=1..90.

FORMULA

a(n)=0, iff n is not in A251964; a(n)=1, iff n is in A251964, but is not A252280;

a(n)=2, iff n is in A251964 & A252980, but is not in A252981, a(n)>=3, iff n is in A251964 & A252980 & A252281.

PROG

(PARI) s(k, pp) = my(sd = sumdigits(pp^k)); sd/2^valuation(sd, 2);

f(n, pp) = {my(p = prime(n), k = 1); while ((sk=s(k, pp)) % p, k++); if (sk == p, k, 0); }

a(n) = {my(pp=prime(n), j=3); while (f(j, pp), j++); j - 3; } \\ Michel Marcus, Dec 09 2018

CROSSREFS

Cf. A000040, A251964, A252280, A252281, A252282, A252283, A252666, A252668.

Sequence in context: A023922 A022064 A225343 * A297813 A156462 A040488

Adjacent sequences:  A252667 A252668 A252669 * A252671 A252672 A252673

KEYWORD

nonn,base

AUTHOR

Vladimir Shevelev, Dec 20 2014

EXTENSIONS

More terms from Michel Marcus, Dec 09 2018

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 13 00:57 EDT 2021. Contains 344980 sequences. (Running on oeis4.)