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 A280641 Numbers k such that k^3 has an odd number of digits and the middle digit is 1. 3
 1, 6, 8, 23, 44, 45, 102, 106, 110, 114, 117, 121, 137, 148, 152, 153, 162, 168, 176, 185, 189, 194, 206, 210, 478, 488, 512, 533, 553, 560, 574, 580, 626, 639, 655, 662, 669, 671, 676, 682, 683, 684, 685, 693, 704, 710, 730, 731, 737, 742, 758, 761, 767, 771 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The sequence of cubes starts: 1, 216, 512, 12167, 85184, 91125, 1061208, 1191016, ... LINKS Lars Blomberg, Table of n, a(n) for n = 1..10000 Jeremy Gardiner, Middle digit in cube numbers, Seqfan Mailing list, Dec 12 2016. EXAMPLE 1^3 = (1), 114^3 = 148(1)544, 560^3 = 1756(1)6000 MATHEMATICA a[n_]:=Part[IntegerDigits[n], (Length[IntegerDigits[n]] + 1)/2]; Select[Range[0, 771], OddQ[Length[IntegerDigits[#^3]]] && a[#^3]==1 &] (* Indranil Ghosh, Mar 06 2017 *) PROG (PARI) isok(k) = my(d=digits(k^3)); (#d%2 == 1) && (d[#d\2 +1] == 1); for(k=0, 771, if(isok(k)==1, print1(k, ", "))); \\ Indranil Ghosh, Mar 06 2017 (Python) i=0 j=1 while i<=771:     n=str(i**3)     l=len(n)     if l%2 and n[(l-1)//2]=="1":         print(str(i), end=', ')         j+=1     i+=1 # Indranil Ghosh, Mar 06 2017 CROSSREFS Cf. A280640, A280642-A280649, A181354. See A279420-A279429 for a k^2 version. See A279430-A279431 for a k^2 version in base 2. Sequence in context: A276226 A034761 A085796 * A005887 A119875 A053189 Adjacent sequences:  A280638 A280639 A280640 * A280642 A280643 A280644 KEYWORD nonn,base,easy AUTHOR Lars Blomberg, Jan 07 2017 STATUS approved

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Last modified May 16 08:07 EDT 2021. Contains 343940 sequences. (Running on oeis4.)