A073771 Highly composite numbers k such that 2*k is not a highly composite number.

4, 36, 48, 240, 720, 1680, 15120, 20160, 45360, 50400, 221760, 498960, 554400, 665280, 2882880, 6486480, 14414400, 17297280, 32432400, 43243200, 110270160, 245044800, 294053760, 735134400, 2095133040, 2205403200, 4655851200

Offset

1,1

Comments

The terms were determined by means of A. Flammenkamp's list (cf. Links); the terms <= 17297280 were confirmed by a PARI program.

Links

Table of n, a(n) for n=1..27.

Achim Flammenkamp Highly Composite Numbers.

Example

36 = A002182(7) is a term since 2*36 = 72 is not highly composite.

Prog

(PARI) {a=1; v=[1]; for(k=1, 40000000, b=numdiv(k); if(b>a, a=b; v=concat(v, k); while(2*v[1]<=k, if(2*v[1]<k, print1(v[1], ", ")); v=vecextract(v, "2.."))))}

Crossrefs

Cf. A002182, A072938.

Sequence in context: A274891 A062182 A308531 * A219247 A224094 A367511

Adjacent sequences: A073768 A073769 A073770 * A073772 A073773 A073774

Keyword

nonn

Author

Klaus Brockhaus, Aug 19 2002

Status

approved