allocate mem(2^30) \\ A055932 Numbers all of whose prime divisors are consecutive primes starting at 2. list(lim, p=2)=my(v=[1], q=nextprime(p+1), t=1); while((t*=p)<=lim, v=concat(v, t*list(lim\t, q))); vecsort(v) \\ Charles R Greathouse IV, Oct 02 2012 toruns(n) = { my (r=[]); while (n, my (v=valuation(n+n%2, 2)); n\=2^v; r=concat(v, r)); r } fromruns(r) = { my (v=0); for (k=1, #r, v=(v+k%2)*2^r[k]-k%2); v } { b = vector(10 001, n, -1); vv = list(11257259750506770); for (n = 1, #vv, v = vv[n]; r = []; forprime (p = 2, oo, if (v==1, a = fromruns(r); if (a+1 <= #b, b[a+1] = n; ); break, e = valuation(v, p); r = concat(e, r); v /= p^e; ); ); ); for (n = 1, #b, if (b[n] >= 0, print (n-1 " " b[n]), break ); ); } quit